scip_expr.c

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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
/*                                                                           */
/*                  This file is part of the program and library             */
/*         SCIP --- Solving Constraint Integer Programs                      */
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/*  Copyright (c) 2002-2023 Zuse Institute Berlin (ZIB)                      */
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/*  you may not use this file except in compliance with the License.         */
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/*  distributed under the License is distributed on an "AS IS" BASIS,        */
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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */

/**@file   scip_expr.c
 * @ingroup OTHER_CFILES
 * @brief  public functions to work with algebraic expressions
 * @author Ksenia Bestuzheva
 * @author Benjamin Mueller
 * @author Felipe Serrano
 * @author Stefan Vigerske
 */

#include <string.h>
#include <ctype.h>

#include "scip/scip_expr.h"
#include "scip/expr.h"
#include "scip/set.h"
#include "scip/misc.h"
#include "scip/scip_copy.h"
#include "scip/scip_mem.h"
#include "scip/scip_message.h"
#include "scip/scip_prob.h"
#include "scip/scip_var.h"
#include "scip/scip_sol.h"
#include "scip/pub_var.h"
#include "scip/struct_scip.h"
#include "scip/struct_mem.h"
#include "scip/struct_stat.h"

/* core expression handler plugins */
#include "scip/expr_value.h"
#include "scip/expr_var.h"
#include "scip/expr_sum.h"
#include "scip/expr_product.h"
#include "scip/expr_pow.h"

/* #define PARSE_DEBUG */

/*lint -e440*/
/*lint -e441*/

/*
 * local functions
 */

/** variable mapping data passed on during copying expressions when copying SCIP instances */
typedef struct
{
   SCIP_HASHMAP*         varmap;             /**< SCIP_HASHMAP mapping variables of the source SCIP to corresponding
                                                  variables of the target SCIP */
   SCIP_HASHMAP*         consmap;            /**< SCIP_HASHMAP mapping constraints of the source SCIP to corresponding
                                                  constraints of the target SCIP */
   SCIP_Bool             global;             /**< should a global or a local copy be created */
   SCIP_Bool             valid;              /**< indicates whether every variable copy was valid */
} COPY_MAPEXPR_DATA;

/** variable expression mapping callback to call when copying expressions (within same or different SCIPs) */
static
SCIP_DECL_EXPR_MAPEXPR(copyVarExpr)
{
   COPY_MAPEXPR_DATA* data;
   SCIP_Bool valid;
   SCIP_VAR* targetvar;

   assert(sourcescip != NULL);
   assert(sourceexpr != NULL);
   assert(targetscip != NULL);
   assert(targetexpr != NULL);
   assert(mapexprdata != NULL);

   *targetexpr = NULL;

   if( !SCIPisExprVar(sourcescip, sourceexpr) )
      return SCIP_OKAY;

   data = (COPY_MAPEXPR_DATA*)mapexprdata;

   SCIP_CALL( SCIPgetVarCopy(sourcescip, targetscip, SCIPgetVarExprVar(sourceexpr), &targetvar, data->varmap,
         data->consmap, data->global, &valid) );
   assert(targetvar != NULL);

   /* if copy was not valid, store so in mapvar data */
   if( !valid )
      data->valid = FALSE;

   SCIP_CALL( SCIPcreateExprVar(targetscip, targetexpr, targetvar, ownercreate, ownercreatedata) );

   return SCIP_OKAY;
}


/** @name Parsing methods (internal)
 * @{
 * Here is an attempt at defining the grammar of an expression.
 * We use upper case names for variables (in the grammar sense) and terminals are between "".
 * Loosely speaking, a Base will be any "block", a Factor is a Base to a power, a Term is a product of Factors
 * and an Expression is a sum of terms.
 * The actual definition:
 * <pre>
 * Expression -> ["+" | "-"] Term { ("+" | "-" | "number *") ] Term }
 * Term       -> Factor { ("*" | "/" ) Factor }
 * Factor     -> Base [ "^" "number" | "^(" "number" ")" ]
 * Base       -> "number" | "<varname>" | "(" Expression ")" | Op "(" OpExpression ")
 * </pre>
 * where [a|b] means a or b or none, (a|b) means a or b, {a} means 0 or more a.
 *
 * Note that Op and OpExpression are undefined. Op corresponds to the name of an expression handler and
 * OpExpression to whatever string the expression handler accepts (through its parse method).
 *
 * parse(Expr|Term|Base) returns an SCIP_EXPR
 *
 * @todo We can change the grammar so that Factor becomes base and we allow a Term to be
 *       <pre> Term       -> Factor { ("*" | "/" | "^") Factor } </pre>
 */

/*lint -emacro(681,debugParse) */
/*lint -emacro(506,debugParse) */
/*lint -emacro(774,debugParse) */
#ifdef PARSE_DEBUG
#define debugParse                      printf
#else
#define debugParse                      while( FALSE ) printf
#endif

/* forward declaration */
static
SCIP_RETCODE parseExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_HASHMAP*         vartoexprvarmap,    /**< hashmap to map between scip vars and var expressions */
   const char*           expr,               /**< expr that we are parsing */
   const char**          newpos,             /**< buffer to store the position of expr where we finished reading */
   SCIP_EXPR**           exprtree,           /**< buffer to store the expr parsed by Expr */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   );

/** Parses base to build a value, variable, sum, or function-like ("func(...)") expression.
 * <pre>
 * Base       -> "number" | "<varname>" | "(" Expression ")" | Op "(" OpExpression ")
 * </pre>
 */
static
SCIP_RETCODE parseBase(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_HASHMAP*         vartoexprvarmap,    /**< hashmap to map between SCIP vars and var expressions */
   const char*           expr,               /**< expr that we are parsing */
   const char**          newpos,             /**< buffer to store the position of expr where we finished reading */
   SCIP_EXPR**           basetree,           /**< buffer to store the expr parsed by Base */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   debugParse("parsing base from %s\n", expr);

   /* ignore whitespace */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );

   if( *expr == '\0' )
   {
      SCIPerrorMessage("Unexpected end of expression string\n");
      return SCIP_READERROR;
   }

   if( *expr == '<' )
   {
      /* parse a variable */
      SCIP_VAR* var;

      SCIP_CALL( SCIPparseVarName(scip, expr, &var, (char**)newpos) );

      if( var == NULL )
      {
         SCIPerrorMessage("Could not find variable with name '%s'\n", expr);
         return SCIP_READERROR;
      }

      expr = *newpos;

      /* check if we have already created an expression out of this var */
      if( SCIPhashmapExists(vartoexprvarmap, (void*)var) )
      {
         debugParse("Variable <%s> has already been parsed, capturing its expression\n", SCIPvarGetName(var));
         *basetree = (SCIP_EXPR*)SCIPhashmapGetImage(vartoexprvarmap, (void*)var);
         SCIPexprCapture(*basetree);
      }
      else
      {
         debugParse("First time parsing variable <%s>, creating varexpr and adding it to hashmap\n", SCIPvarGetName(var));
         /* intentionally not using createExprVar here, since parsed expressions are not part of a constraint
          * (they will be copied when a constraint is created)
          */
         SCIP_CALL( SCIPcreateExprVar(scip, basetree, var, ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPhashmapInsert(vartoexprvarmap, (void*)var, (void*)(*basetree)) );
      }
   }
   else if( *expr == '(' )
   {
      /* parse expression */
      SCIP_CALL( parseExpr(scip, vartoexprvarmap, ++expr, newpos, basetree, ownercreate, ownercreatedata) );
      expr = *newpos;

      /* expect ')' */
      if( *expr != ')' )
      {
         SCIPerrorMessage("Read a '(', parsed expression inside --> expecting closing ')'. Got <%c>: rest of string <%s>\n", *expr, expr);
         SCIP_CALL( SCIPreleaseExpr(scip, basetree) );
         return SCIP_READERROR;
      }
      ++expr;
      debugParse("Done parsing expression, continue with <%s>\n", expr);
   }
   else if( isdigit(*expr) )
   {
      /* parse number */
      SCIP_Real value;
      if( !SCIPstrToRealValue(expr, &value, (char**)&expr) )
      {
         SCIPerrorMessage("error parsing number from <%s>\n", expr);
         return SCIP_READERROR;
      }
      debugParse("Parsed value %g, creating a value-expression.\n", value);
      SCIP_CALL( SCIPcreateExprValue(scip, basetree, value, ownercreate, ownercreatedata) );
   }
   else if( isalpha(*expr) )
   {
      /* a (function) name is coming, should find exprhandler with such name */
      int i;
      char operatorname[SCIP_MAXSTRLEN];
      SCIP_EXPRHDLR* exprhdlr;
      SCIP_Bool success;

      /* get name */
      i = 0;
      while( *expr != '(' && *expr != '\0' && !isspace(*expr)
             && !( *expr == '\\' && *(expr+1) != '\0' && strchr(SCIP_SPACECONTROL, *(expr+1)) ) )
      {
         operatorname[i] = *expr;
         ++expr;
         ++i;
      }
      operatorname[i] = '\0';

      /* after name we must see a '(' */
      if( *expr != '(' )
      {
         SCIPerrorMessage("Expected '(' after operator name <%s>, but got %s.\n", operatorname, expr);
         return SCIP_READERROR;
      }

      /* search for expression handler */
      exprhdlr = SCIPfindExprhdlr(scip, operatorname);

      /* check expression handler exists and has a parsing method */
      if( exprhdlr == NULL )
      {
         SCIPerrorMessage("No expression handler with name <%s> found.\n", operatorname);
         return SCIP_READERROR;
      }

      ++expr;
      SCIP_CALL( SCIPexprhdlrParseExpr(exprhdlr, scip->set, expr, newpos, basetree, &success, ownercreate, ownercreatedata) );

      if( !success )
      {
         SCIPerrorMessage("Error while expression handler <%s> was parsing %s\n", operatorname, expr);
         assert(*basetree == NULL);
         return SCIP_READERROR;
      }
      expr = *newpos;

      /* we should see the ')' of Op "(" OpExpression ") */
      assert(*expr == ')');

      /* move one character forward */
      ++expr;
   }
   else
   {
      /* Base -> "number" | "<varname>" | "(" Expression ")" | Op "(" OpExpression ") */
      SCIPerrorMessage("Expected a number, (expression), <varname>, Opname(Opexpr), instead got <%c> from %s\n", *expr, expr);
      return SCIP_READERROR;
   }

   *newpos = expr;

   return SCIP_OKAY;
}

/** Parses a factor and builds a product-expression if there is an exponent, otherwise returns the base expression.
 * <pre>
 * Factor -> Base [ "^" "number" | "^(" "number" ")" ]
 * </pre>
 */
static
SCIP_RETCODE parseFactor(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_Bool             isdenominator,      /**< whether factor is in the denominator */
   SCIP_HASHMAP*         vartoexprvarmap,    /**< hashmap to map between scip vars and var expressions */
   const char*           expr,               /**< expr that we are parsing */
   const char**          newpos,             /**< buffer to store the position of expr where we finished reading */
   SCIP_EXPR**           factortree,         /**< buffer to store the expr parsed by Factor */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   SCIP_EXPR*  basetree;
   SCIP_Real exponent;

   debugParse("parsing factor from %s\n", expr);

   if( *expr == '\0' )
   {
      SCIPerrorMessage("Unexpected end of expression string.\n");
      return SCIP_READERROR;
   }

   /* parse Base */
   /* ignore whitespace */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );

   SCIP_CALL( parseBase(scip, vartoexprvarmap, expr, newpos, &basetree, ownercreate, ownercreatedata) );
   expr = *newpos;

   /* check if there is an exponent */
   /* ignore whitespace */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );

   if( *expr == '^' )
   {
      ++expr;
      SCIP_CALL( SCIPskipSpace((char**)&expr) );

      if( *expr == '\0' )
      {
         SCIPerrorMessage("Unexpected end of expression string after '^'.\n");
         SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
         return SCIP_READERROR;
      }

      if( *expr == '(' )
      {
         ++expr;

         /* it is exponent with parenthesis; expect number possibly starting with + or - */
         if( !SCIPstrToRealValue(expr, &exponent, (char**)&expr) )
         {
            SCIPerrorMessage("error parsing number from <%s>\n", expr);
            SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
            return SCIP_READERROR;
         }

         /* expect the ')' */
         SCIP_CALL( SCIPskipSpace((char**)&expr) );
         if( *expr != ')' )
         {
            SCIPerrorMessage("error in parsing exponent: expected ')', received <%c> from <%s>\n", *expr,  expr);
            SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
            return SCIP_READERROR;
         }
         ++expr;
      }
      else
      {
         /* no parenthesis, we should see just a positive number */

         /* expect a digit */
         if( isdigit(*expr) )
         {
            if( !SCIPstrToRealValue(expr, &exponent, (char**)&expr) )
            {
               SCIPerrorMessage("error parsing number from <%s>\n", expr);
               SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
               return SCIP_READERROR;
            }
         }
         else
         {
            SCIPerrorMessage("error in parsing exponent, expected a digit, received <%c> from <%s>\n", *expr,  expr);
            SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
            return SCIP_READERROR;
         }
      }

      debugParse("parsed the exponent %g\n", exponent); /*lint !e506 !e681*/
   }
   else
   {
      /* there is no explicit exponent */
      exponent = 1.0;
   }
   *newpos = expr;

   /* multiply with -1 when we are in the denominator */
   if( isdenominator )
      exponent *= -1.0;

   /* create power */
   if( exponent != 1.0 )
   {
      SCIP_CALL( SCIPcreateExprPow(scip, factortree, basetree, exponent, ownercreate, ownercreatedata) );
      SCIP_CALL( SCIPreleaseExpr(scip, &basetree) );
   }
   else
      /* Factor consists of this unique Base */
      *factortree = basetree;

   return SCIP_OKAY;
}

/** Parses a term and builds a product-expression, where each factor is a child.
 * <pre>
 * Term -> Factor { ("*" | "/" ) Factor }
 * </pre>
 */
static
SCIP_RETCODE parseTerm(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_HASHMAP*         vartoexprvarmap,    /**< hashmap to map between scip vars and var expressions */
   const char*           expr,               /**< expr that we are parsing */
   const char**          newpos,             /**< buffer to store the position of expr where we finished reading */
   SCIP_EXPR**           termtree,           /**< buffer to store the expr parsed by Term */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   SCIP_EXPR* factortree;

   debugParse("parsing term from %s\n", expr);

   /* parse Factor */
   /* ignore whitespace */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );

   SCIP_CALL( parseFactor(scip, FALSE, vartoexprvarmap, expr, newpos, &factortree, ownercreate, ownercreatedata) );
   expr = *newpos;

   debugParse("back to parsing Term, continue parsing from %s\n", expr);

   /* check if Terms has another Factor incoming */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );
   if( *expr == '*' || *expr == '/' )
   {
      /* initialize termtree as a product expression with a single term, so we can append the extra Factors */
      SCIP_CALL( SCIPcreateExprProduct(scip, termtree, 1, &factortree, 1.0, ownercreate, ownercreatedata) );
      SCIP_CALL( SCIPreleaseExpr(scip, &factortree) );

      /* loop: parse Factor, find next symbol */
      do
      {
         SCIP_RETCODE retcode;
         SCIP_Bool isdivision;

         isdivision = (*expr == '/') ? TRUE : FALSE;

         debugParse("while parsing term, read char %c\n", *expr); /*lint !e506 !e681*/

         ++expr;
         retcode = parseFactor(scip, isdivision, vartoexprvarmap, expr, newpos, &factortree, ownercreate, ownercreatedata);

         /* release termtree, if parseFactor fails with a read-error */
         if( retcode == SCIP_READERROR )
         {
            SCIP_CALL( SCIPreleaseExpr(scip, termtree) );
         }
         SCIP_CALL( retcode );

         /* append newly created factor */
         SCIP_CALL( SCIPappendExprChild(scip, *termtree, factortree) );
         SCIP_CALL( SCIPreleaseExpr(scip, &factortree) );

         /* find next symbol */
         expr = *newpos;
         SCIP_CALL( SCIPskipSpace((char**)&expr) );
      }
      while( *expr == '*' || *expr == '/' );
   }
   else
   {
      /* Term consists of this unique factor */
      *termtree = factortree;
   }

   *newpos = expr;

   return SCIP_OKAY;
}

/** parses an expression and builds a sum-expression with children
 *
 * <pre>
 * Expression -> ["+" | "-"] Term { ("+" | "-" | "number *") ] Term }
 * </pre>
 */
static
SCIP_RETCODE parseExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_HASHMAP*         vartoexprvarmap,    /**< hashmap to map between scip vars and var expressions */
   const char*           expr,               /**< expr that we are parsing */
   const char**          newpos,             /**< buffer to store the position of expr where we finished reading */
   SCIP_EXPR**           exprtree,           /**< buffer to store the expr parsed by Expr */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   SCIP_Real sign;
   SCIP_EXPR* termtree;

   debugParse("parsing expression %s\n", expr); /*lint !e506 !e681*/

   /* ignore whitespace */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );

   /* if '+' or '-', store it */
   sign = 1.0;
   if( *expr == '+' || *expr == '-' )
   {
      debugParse("while parsing expression, read char %c\n", *expr); /*lint !e506 !e681*/
      sign = *expr == '+' ? 1.0 : -1.0;
      ++expr;
   }

   SCIP_CALL( parseTerm(scip, vartoexprvarmap, expr, newpos, &termtree, ownercreate, ownercreatedata) );
   expr = *newpos;

   debugParse("back to parsing expression (we have the following term), continue parsing from %s\n", expr); /*lint !e506 !e681*/

   /* check if Expr has another Term incoming */
   SCIP_CALL( SCIPskipSpace((char**)&expr) );
   if( *expr == '+' || *expr == '-' )
   {
      if( SCIPexprIsValue(scip->set, termtree) )
      {
         /* initialize exprtree as a sum expression with a constant only, so we can append the following terms */
         SCIP_CALL( SCIPcreateExprSum(scip, exprtree, 0, NULL, NULL, sign * SCIPgetValueExprValue(termtree), ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPreleaseExpr(scip, &termtree) );
      }
      else
      {
         /* initialize exprtree as a sum expression with a single term, so we can append the following terms */
         SCIP_CALL( SCIPcreateExprSum(scip, exprtree, 1, &termtree, &sign, 0.0, ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPreleaseExpr(scip, &termtree) );
      }

      /* loop: parse Term, find next symbol */
      do
      {
         SCIP_RETCODE retcode;
         SCIP_Real coef;

         /* check if we have a "coef * <term>" */
         if( SCIPstrToRealValue(expr, &coef, (char**)newpos) )
         {
            SCIP_CALL( SCIPskipSpace((char**)newpos) );

            if( **newpos != '*' )
            {
               /* no '*', so fall back to parsing term after sign */
               coef = (*expr == '+') ? 1.0 : -1.0;
               ++expr;
            }
            else
            {
               /* keep coefficient in coef and continue parsing term after coefficient */
               expr = (*newpos)+1;

               SCIP_CALL( SCIPskipSpace((char**)&expr) );
            }
         }
         else
         {
            coef = (*expr == '+') ? 1.0 : -1.0;
            ++expr;
         }

         debugParse("while parsing expression, read coefficient %g\n", coef); /*lint !e506 !e681*/

         retcode = parseTerm(scip, vartoexprvarmap, expr, newpos, &termtree, ownercreate, ownercreatedata);

         /* release exprtree if parseTerm fails with an read-error */
         if( retcode == SCIP_READERROR )
         {
            SCIP_CALL( SCIPreleaseExpr(scip, exprtree) );
         }
         SCIP_CALL( retcode );

         /* append newly created term */
         SCIP_CALL( SCIPappendExprSumExpr(scip, *exprtree, termtree, coef) );
         SCIP_CALL( SCIPreleaseExpr(scip, &termtree) );

         /* find next symbol */
         expr = *newpos;
         SCIP_CALL( SCIPskipSpace((char**)&expr) );
      } while( *expr == '+' || *expr == '-' );
   }
   else
   {
      /* Expr consists of this unique ['+' | '-'] Term */
      if( sign  < 0.0 )
      {
         assert(sign == -1.0);
         SCIP_CALL( SCIPcreateExprSum(scip, exprtree, 1, &termtree, &sign, 0.0, ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPreleaseExpr(scip, &termtree) );
      }
      else
         *exprtree = termtree;
   }

   *newpos = expr;

   return SCIP_OKAY;
}

/** @} */  /* end of parsing methods */

/** @name Simplify methods (internal)
 * @{
 */

/** returns an equivalent expression for a given expression if possible
 *
 * it adds the expression to key2expr if the map does not contain the key
 */
static
SCIP_RETCODE findEqualExpr(
   SCIP_SET*             set,                /**< global SCIP settings */
   SCIP_EXPR*            expr,               /**< expression to replace */
   SCIP_MULTIHASH*       key2expr,           /**< mapping of hashes to expressions */
   SCIP_EXPR**           newexpr             /**< pointer to store an equivalent expression (NULL if there is none) */
   )
{  /*lint --e{438}*/
   SCIP_MULTIHASHLIST* multihashlist;

   assert(set != NULL);
   assert(expr != NULL);
   assert(key2expr != NULL);
   assert(newexpr != NULL);

   *newexpr = NULL;
   multihashlist = NULL;
   do
   {
      /* search for an equivalent expression */
      *newexpr = (SCIP_EXPR*)(SCIPmultihashRetrieveNext(key2expr, &multihashlist, (void*)expr));

      if( *newexpr == NULL )
      {
         /* processed all expressions like expr from hash table, so insert expr */
         SCIP_CALL( SCIPmultihashInsert(key2expr, (void*) expr) );
         break;
      }
      else if( expr != *newexpr )
      {
         assert(SCIPexprCompare(set, expr, *newexpr) == 0);
         break;
      }
      else
      {
         /* can not replace expr since it is already contained in the hashtablelist */
         assert(expr == *newexpr);
         *newexpr = NULL;
         break;
      }
   }
   while( TRUE ); /*lint !e506*/

   return SCIP_OKAY;
}

/** userdata for multihash for common subexpression */
typedef struct
{
   SCIP_SET*      set;
   SCIP_EXPRITER* hashiterator;
} COMMONSUBEXPR_HASH_DATA;

/** get key of hash element */
static
SCIP_DECL_HASHGETKEY(hashCommonSubexprGetKey)
{
   return elem;
}  /*lint !e715*/

/** checks if two expressions are structurally the same */
static
SCIP_DECL_HASHKEYEQ(hashCommonSubexprEq)
{
   COMMONSUBEXPR_HASH_DATA* data;
   SCIP_EXPR* expr1;
   SCIP_EXPR* expr2;

   data = (COMMONSUBEXPR_HASH_DATA*)userptr;
   assert(data != NULL);

   expr1 = (SCIP_EXPR*)key1;
   expr2 = (SCIP_EXPR*)key2;
   assert(expr1 != NULL);
   assert(expr2 != NULL);

   return expr1 == expr2 || SCIPexprCompare(data->set, expr1, expr2) == 0;
}  /*lint !e715*/

/** get value of hash element when comparing with another expression */
static
SCIP_DECL_HASHKEYVAL(hashCommonSubexprKeyval)
{
   COMMONSUBEXPR_HASH_DATA* data;
   SCIP_EXPR* expr;

   expr = (SCIP_EXPR*) key;
   assert(expr != NULL);

   data = (COMMONSUBEXPR_HASH_DATA*) userptr;
   assert(data != NULL);

   return SCIPexpriterGetExprUserData(data->hashiterator, expr).uintval;
}  /*lint !e715*/

/** hashes an expression using an already existing iterator
 *
 * The iterator must by of type DFS with allowrevisit=FALSE and only the leaveexpr stage enabled.
 * The hashes of all visited expressions will be stored in the iterators expression data.
 */
static
SCIP_RETCODE hashExpr(
   SCIP_SET*             set,                /**< global SCIP settings */
   BMS_BUFMEM*           bufmem,             /**< buffer memory */
   SCIP_EXPR*            expr,               /**< expression to hash */
   SCIP_EXPRITER*        hashiterator,       /**< iterator to use for hashing */
   int*                  nvisitedexprs       /**< counter to increment by the number of expressions visited, or NULL */
   )
{
   SCIP_EXPRITER_USERDATA iterdata;
   unsigned int* childrenhashes;
   int childrenhashessize;
   int i;

   assert(set != NULL);
   assert(expr != NULL);
   assert(hashiterator != NULL);

   childrenhashessize = 5;
   SCIP_ALLOC( BMSallocBufferMemoryArray(bufmem, &childrenhashes, childrenhashessize) );

   for( expr = SCIPexpriterRestartDFS(hashiterator, expr); !SCIPexpriterIsEnd(hashiterator); expr = SCIPexpriterGetNext(hashiterator) ) /*lint !e441*/
   {
      assert(SCIPexpriterGetStageDFS(hashiterator) == SCIP_EXPRITER_LEAVEEXPR);

      if( nvisitedexprs != NULL )
         ++*nvisitedexprs;

      /* collect hashes of children */
      if( childrenhashessize < SCIPexprGetNChildren(expr) )
      {
         childrenhashessize = SCIPsetCalcMemGrowSize(set, SCIPexprGetNChildren(expr));
         SCIP_ALLOC( BMSreallocBufferMemoryArray(bufmem, &childrenhashes, childrenhashessize) );
      }
      for( i = 0; i < SCIPexprGetNChildren(expr); ++i )
         childrenhashes[i] = SCIPexpriterGetExprUserData(hashiterator, SCIPexprGetChildren(expr)[i]).uintval;

      SCIP_CALL( SCIPexprhdlrHashExpr(SCIPexprGetHdlr(expr), set, expr, &iterdata.uintval, childrenhashes) );

      SCIPexpriterSetCurrentUserData(hashiterator, iterdata);
   }

   BMSfreeBufferMemoryArray(bufmem, &childrenhashes);

   return SCIP_OKAY;
}

/** @} */  /* end of simplify methods */

/*
 * public functions
 */

/**@addtogroup PublicExprHandlerMethods
 * @{
 */

#ifdef NDEBUG
#undef SCIPgetExprhdlrs
#undef SCIPgetNExprhdlrs
#undef SCIPfindExprhdlr
#undef SCIPgetExprhdlrVar
#undef SCIPgetExprhdlrValue
#undef SCIPgetExprhdlrSum
#undef SCIPgetExprhdlrProduct
#undef SCIPgetExprhdlrPower
#endif

/** creates the handler for an expression handler and includes it into SCIP */
SCIP_RETCODE SCIPincludeExprhdlr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRHDLR**       exprhdlr,           /**< buffer where to store created expression handler */
   const char*           name,               /**< name of expression handler (must not be NULL) */
   const char*           desc,               /**< description of expression handler (can be NULL) */
   unsigned int          precedence,         /**< precedence of expression operation (used for printing) */
   SCIP_DECL_EXPREVAL((*eval)),              /**< point evaluation callback (must not be NULL) */
   SCIP_EXPRHDLRDATA*    data                /**< data of expression handler (can be NULL) */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(exprhdlr != NULL);

   SCIP_CALL( SCIPexprhdlrCreate(scip->mem->setmem, exprhdlr, name, desc, precedence, eval, data) );
   assert(*exprhdlr != NULL);

   SCIP_CALL( SCIPsetIncludeExprhdlr(scip->set, *exprhdlr) );

   return SCIP_OKAY;
}

/** gives expression handlers */
SCIP_EXPRHDLR** SCIPgetExprhdlrs(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrs;
}

/** gives number of expression handlers */
int SCIPgetNExprhdlrs(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->nexprhdlrs;
}

/** returns an expression handler of a given name (or NULL if not found) */
SCIP_EXPRHDLR* SCIPfindExprhdlr(
   SCIP*                 scip,               /**< SCIP data structure */
   const char*           name                /**< name of expression handler */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return SCIPsetFindExprhdlr(scip->set, name);
}

/** returns expression handler for variable expressions (or NULL if not included) */
SCIP_EXPRHDLR* SCIPgetExprhdlrVar(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrvar;
}

/** returns expression handler for constant value expressions (or NULL if not included) */
SCIP_EXPRHDLR* SCIPgetExprhdlrValue(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrval;
}

/** returns expression handler for sum expressions (or NULL if not included) */
SCIP_EXPRHDLR* SCIPgetExprhdlrSum(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrsum;
}

/** returns expression handler for product expressions (or NULL if not included) */
SCIP_EXPRHDLR* SCIPgetExprhdlrProduct(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrproduct;
}

/** returns expression handler for power expressions (or NULL if not included) */
SCIP_EXPRHDLR* SCIPgetExprhdlrPower(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   return scip->set->exprhdlrpow;
}

/**@} */


/**@name Expression Methods */
/**@{ */

#ifdef NDEBUG
#undef SCIPappendExprChild
#undef SCIPreplaceExprChild
#undef SCIPremoveExprChildren
#undef SCIPduplicateExpr
#undef SCIPduplicateExprShallow
#undef SCIPcaptureExpr
#undef SCIPreleaseExpr
#undef SCIPisExprVar
#undef SCIPisExprValue
#undef SCIPisExprSum
#undef SCIPisExprProduct
#undef SCIPisExprPower
#undef SCIPprintExpr
#undef SCIPevalExpr
#undef SCIPgetExprNewSoltag
#undef SCIPevalExprGradient
#undef SCIPevalExprHessianDir
#undef SCIPevalExprActivity
#undef SCIPcompareExpr
#undef SCIPsimplifyExpr
#undef SCIPcallExprCurvature
#undef SCIPcallExprMonotonicity
#undef SCIPcallExprEval
#undef SCIPcallExprEvalFwdiff
#undef SCIPcallExprInteval
#undef SCIPcallExprEstimate
#undef SCIPcallExprInitestimates
#undef SCIPcallExprSimplify
#undef SCIPcallExprReverseprop
#endif

/** creates and captures an expression with given expression data and children */
SCIP_RETCODE SCIPcreateExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr,               /**< pointer where to store expression */
   SCIP_EXPRHDLR*        exprhdlr,           /**< expression handler */
   SCIP_EXPRDATA*        exprdata,           /**< expression data (expression assumes ownership) */
   int                   nchildren,          /**< number of children */
   SCIP_EXPR**           children,           /**< children (can be NULL if nchildren is 0) */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(scip->set != NULL);

   SCIP_CALL( SCIPexprCreate(scip->set, scip->mem->probmem, expr, exprhdlr, exprdata, nchildren, children, ownercreate,
         ownercreatedata) );

   return SCIP_OKAY;
}

/** creates and captures an expression with given expression data and up to two children */
SCIP_RETCODE SCIPcreateExpr2(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr,               /**< pointer where to store expression */
   SCIP_EXPRHDLR*        exprhdlr,           /**< expression handler */
   SCIP_EXPRDATA*        exprdata,           /**< expression data */
   SCIP_EXPR*            child1,             /**< first child (can be NULL) */
   SCIP_EXPR*            child2,             /**< second child (can be NULL) */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(expr != NULL);
   assert(exprhdlr != NULL);

   if( child1 != NULL && child2 != NULL )
   {
      SCIP_EXPR* pair[2];
      pair[0] = child1;
      pair[1] = child2;

      SCIP_CALL( SCIPcreateExpr(scip, expr, exprhdlr, exprdata, 2, pair, ownercreate, ownercreatedata) );
   }
   else if( child2 == NULL )
   {
      SCIP_CALL( SCIPcreateExpr(scip, expr, exprhdlr, exprdata, child1 == NULL ? 0 : 1, &child1, ownercreate,
            ownercreatedata) );
   }
   else
   {
      /* child2 != NULL, child1 == NULL */
      SCIP_CALL( SCIPcreateExpr(scip, expr, exprhdlr, exprdata, 1, &child2, ownercreate, ownercreatedata) );
   }

   return SCIP_OKAY;
}

/** creates and captures an expression representing a quadratic function */
SCIP_RETCODE SCIPcreateExprQuadratic(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr,               /**< pointer where to store expression */
   int                   nlinvars,           /**< number of linear terms */
   SCIP_VAR**            linvars,            /**< array with variables in linear part */
   SCIP_Real*            lincoefs,           /**< array with coefficients of variables in linear part */
   int                   nquadterms,         /**< number of quadratic terms */
   SCIP_VAR**            quadvars1,          /**< array with first variables in quadratic terms */
   SCIP_VAR**            quadvars2,          /**< array with second variables in quadratic terms */
   SCIP_Real*            quadcoefs,          /**< array with coefficients of quadratic terms */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   SCIP_EXPR** children;
   SCIP_Real* coefs;
   int i;

   assert(scip != NULL);
   assert(expr != NULL);
   assert(nlinvars == 0 || (linvars != NULL && lincoefs != NULL));
   assert(nquadterms == 0 || (quadvars1 != NULL && quadvars2 != NULL && quadcoefs != NULL));

   /* allocate memory */
   SCIP_CALL( SCIPallocBufferArray(scip, &children, nquadterms + nlinvars) );
   SCIP_CALL( SCIPallocBufferArray(scip, &coefs, nquadterms + nlinvars) );

   /* create children for quadratic terms */
   for( i = 0; i < nquadterms; ++i )
   {
      assert(quadvars1 != NULL && quadvars1[i] != NULL);
      assert(quadvars2 != NULL && quadvars2[i] != NULL);

      /* quadratic term */
      if( quadvars1[i] == quadvars2[i] )
      {
         SCIP_EXPR* xexpr;

         /* create variable expression; intentionally not using createExprVar here,
          * since expression created here is not part of a constraint (they will be copied when a constraint is created)
          */
         SCIP_CALL( SCIPcreateExprVar(scip, &xexpr, quadvars1[i], ownercreate, ownercreatedata) );

         /* create pow expression */
         SCIP_CALL( SCIPcreateExprPow(scip, &children[i], xexpr, 2.0, ownercreate, ownercreatedata) );

         /* release variable expression; note that the variable expression is still captured by children[i] */
         SCIP_CALL( SCIPreleaseExpr(scip, &xexpr) );
      }
      else /* bilinear term */
      {
         SCIP_EXPR* exprs[2];

         /* create variable expressions; intentionally not using createExprVar here,
          * since expression created here is not part of a constraint (they will be copied when a constraint is created)
          */
         SCIP_CALL( SCIPcreateExprVar(scip, &exprs[0], quadvars1[i], ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPcreateExprVar(scip, &exprs[1], quadvars2[i], ownercreate, ownercreatedata) );

         /* create product expression */
         SCIP_CALL( SCIPcreateExprProduct(scip, &children[i], 2, exprs, 1.0, ownercreate, ownercreatedata) );

         /* release variable expressions; note that the variable expressions are still captured by children[i] */
         SCIP_CALL( SCIPreleaseExpr(scip, &exprs[1]) );
         SCIP_CALL( SCIPreleaseExpr(scip, &exprs[0]) );
      }

      /* store coefficient */
      coefs[i] = quadcoefs[i];
   }

   /* create children for linear terms */
   for( i = 0; i < nlinvars; ++i )
   {
      assert(linvars != NULL && linvars[i] != NULL);

      /* create variable expression; intentionally not using createExprVar here,
       * since expression created here is not part of a constraint (they will be copied when a constraint is created);
       * release variable expression after the sum expression has been created
       */
      SCIP_CALL( SCIPcreateExprVar(scip, &children[nquadterms + i], linvars[i], ownercreate, ownercreatedata) );

      /* store coefficient */
      coefs[nquadterms + i] = lincoefs[i];
   }

   /* create sum expression */
   SCIP_CALL( SCIPcreateExprSum(scip, expr, nquadterms + nlinvars, children, coefs, 0.0, ownercreate, ownercreatedata) );

   /* release children */
   for( i = 0; i < nquadterms + nlinvars; ++i )
   {
      assert(children[i] != NULL);
      SCIP_CALL( SCIPreleaseExpr(scip, &children[i]) );
   }

   /* free memory */
   SCIPfreeBufferArray(scip, &coefs);
   SCIPfreeBufferArray(scip, &children);

   return SCIP_OKAY;
}

/** creates and captures an expression representing a monomial
 *
 * @note In deviation from the actual definition of monomials, we also allow for negative and rational exponents.
 * So this function actually creates an expression for a signomial that has exactly one term.
 */
SCIP_RETCODE SCIPcreateExprMonomial(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr,               /**< pointer where to store expression */
   int                   nfactors,           /**< number of factors in monomial */
   SCIP_VAR**            vars,               /**< variables in the monomial */
   SCIP_Real*            exponents,          /**< exponent in each factor, or NULL if all 1.0 */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(expr != NULL);
   assert(nfactors >= 0);

   /* return 1 as constant expression if there are no factors */
   if( nfactors == 0 )
   {
      SCIP_CALL( SCIPcreateExprValue(scip, expr, 1.0, ownercreate, ownercreatedata) );
   }
   else if( nfactors == 1 )
   {
      /* only one factor and exponent is 1 => return factors[0] */
      if( exponents == NULL || exponents[0] == 1.0 )
      {
         /* intentionally not using createExprVar here, since expression created here is not part of
          * a constraint (they will be copied when a constraint is created)
          */
         SCIP_CALL( SCIPcreateExprVar(scip, expr, vars[0], ownercreate, ownercreatedata) );
      }
      else
      {
         SCIP_EXPR* varexpr;

         /* create variable and power expression; intentionally not using createExprVar here,
          * since expression created here is not part of a constraint (they will be copied when a constraint is created)
          */
         SCIP_CALL( SCIPcreateExprVar(scip, &varexpr, vars[0], ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPcreateExprPow(scip, expr, varexpr, exponents[0], ownercreate, ownercreatedata) );
         SCIP_CALL( SCIPreleaseExpr(scip, &varexpr) );
      }
   }
   else
   {
      SCIP_EXPR** children;
      int i;

      /* allocate memory to store the children */
      SCIP_CALL( SCIPallocBufferArray(scip, &children, nfactors) );

      /* create children */
      for( i = 0; i < nfactors; ++i )
      {
         /* check whether to create a power expression or not, i.e., exponent == 1 */
         if( exponents == NULL || exponents[i] == 1.0 )
         {
            SCIP_CALL( SCIPcreateExprVar(scip, &children[i], vars[i], ownercreate, ownercreatedata) );
         }
         else
         {
            SCIP_EXPR* varexpr;

            /* create variable and pow expression */
            SCIP_CALL( SCIPcreateExprVar(scip, &varexpr, vars[i], ownercreate, ownercreatedata) );
            SCIP_CALL( SCIPcreateExprPow(scip, &children[i], varexpr, exponents[i], ownercreate, ownercreatedata) );
            SCIP_CALL( SCIPreleaseExpr(scip, &varexpr) );
         }
      }

      /* create product expression */
      SCIP_CALL( SCIPcreateExprProduct(scip, expr, nfactors, children, 1.0, ownercreate, ownercreatedata) );

      /* release children */
      for( i = 0; i < nfactors; ++i )
      {
         assert(children[i] != NULL);
         SCIP_CALL( SCIPreleaseExpr(scip, &children[i]) );
      }

      /* free memory */
      SCIPfreeBufferArray(scip, &children);
   }

   return SCIP_OKAY;
}

/** appends child to the children list of expr
 *
 * @attention Only use if you really know what you are doing. The expression handler of the expression needs to be able to handle an increase in the number of children.
 */
SCIP_RETCODE SCIPappendExprChild(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression */
   SCIP_EXPR*            child               /**< expression to be appended */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprAppendChild(scip->set, scip->mem->probmem, expr, child) );

   return SCIP_OKAY;
}

/** overwrites/replaces a child of an expressions
 *
 * The old child is released and the newchild is captured, unless they are the same (=same pointer).
 */
SCIP_RETCODE SCIPreplaceExprChild(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression which is going to replace a child */
   int                   childidx,           /**< index of child being replaced */
   SCIP_EXPR*            newchild            /**< the new child */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprReplaceChild(scip->set, scip->stat, scip->mem->probmem, expr, childidx, newchild) );

   return SCIP_OKAY;
}

/** remove all children of expr
 *
 * @attention Only use if you really know what you are doing. The expression handler of the expression needs to be able to handle the removal of all children.
 */
SCIP_RETCODE SCIPremoveExprChildren(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprRemoveChildren(scip->set, scip->stat, scip->mem->probmem, expr) );

   return SCIP_OKAY;
}

/** duplicates the given expression and its children */
SCIP_RETCODE SCIPduplicateExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< original expression */
   SCIP_EXPR**           copyexpr,           /**< buffer to store duplicate of expr */
   SCIP_DECL_EXPR_MAPEXPR((*mapexpr)),       /**< expression mapping function, or NULL for creating new expressions */
   void*                 mapexprdata,        /**< data of expression mapping function */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call on expression copy to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprCopy(scip->set, scip->stat, scip->mem->probmem, scip->set, scip->stat, scip->mem->probmem,
         expr, copyexpr, mapexpr, mapexprdata, ownercreate, ownercreatedata) );

   return SCIP_OKAY;
}

/** duplicates the given expression, but reuses its children */
SCIP_RETCODE SCIPduplicateExprShallow(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< original expression */
   SCIP_EXPR**           copyexpr,           /**< buffer to store (shallow) duplicate of expr */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprDuplicateShallow(scip->set, scip->mem->probmem, expr, copyexpr, ownercreate, ownercreatedata) );

   return SCIP_OKAY;
}

/** copies an expression including children to use in a (possibly different) SCIP instance */
SCIP_RETCODE SCIPcopyExpr(
   SCIP*                 sourcescip,         /**< source SCIP data structure */
   SCIP*                 targetscip,         /**< target SCIP data structure */
   SCIP_EXPR*            expr,               /**< original expression */
   SCIP_EXPR**           copyexpr,           /**< buffer to store duplicate of expr */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call on expression copy to create ownerdata */
   void*                 ownercreatedata,    /**< data to pass to ownercreate */
   SCIP_HASHMAP*         varmap,             /**< a SCIP_HASHMAP mapping variables of the source SCIP to the corresponding
                                              *   variables of the target SCIP, or NULL */
   SCIP_HASHMAP*         consmap,            /**< a hashmap to store the mapping of source constraints to the corresponding
                                              *   target constraints, or NULL */
   SCIP_Bool             global,             /**< create a global or a local copy? */
   SCIP_Bool*            valid               /**< pointer to store whether all checked or enforced constraints were validly copied */
   )
{
#ifndef _MSC_VER
   COPY_MAPEXPR_DATA copydata = {
      .varmap = varmap,
      .consmap = consmap,
      .global = global,
      .valid = TRUE
   };
#else  /* MS compiler doesn't have proper C99 support... */
   COPY_MAPEXPR_DATA copydata;
   copydata.varmap = varmap;
   copydata.consmap = consmap;
   copydata.global = global;
   copydata.valid = TRUE;
#endif

   assert(sourcescip != NULL);
   assert(sourcescip->mem != NULL);
   assert(targetscip != NULL);
   assert(targetscip->mem != NULL);

   SCIP_CALL( SCIPexprCopy(sourcescip->set, sourcescip->stat, sourcescip->mem->probmem,
      targetscip->set, targetscip->stat, targetscip->mem->probmem,
      expr, copyexpr, copyVarExpr, &copydata, ownercreate, ownercreatedata) );

   *valid = copydata.valid;

   return SCIP_OKAY;
}

/** creates an expression from a string
 *
 * We specify the grammar that defines the syntax of an expression.
 * Loosely speaking, a `Base` will be any "block", a `Factor` is a `Base` to a power,
 * a `Term` is a product of `Factors` and an `Expression` is a sum of `Terms`.
 *
 * The actual definition:
 * <pre>
 * Expression -> ["+" | "-"] Term { ("+" | "-" | "number *") ] Term }
 * Term       -> Factor { ("*" | "/" ) Factor }
 * Factor     -> Base [ "^" "number" | "^(" "number" ")" ]
 * Base       -> "number" | "<varname>" | "(" Expression ")" | Op "(" OpExpression ")
 * </pre>
 * where `[a|b]` means `a` or `b` or none, `(a|b)` means `a` or `b`, `{a}` means 0 or more `a`.
 *
 * Note that `Op` and `OpExpression` are undefined.
 * `Op` corresponds to the name of an expression handler and `OpExpression` to whatever string the expression handler accepts (through its parse method).
 */
SCIP_RETCODE SCIPparseExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr,               /**< pointer to store the expr parsed */
   const char*           exprstr,            /**< string with the expr to parse */
   const char**          finalpos,           /**< buffer to store the position of exprstr where we finished reading, or NULL if not of interest */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   const char* finalpos_;
   SCIP_RETCODE retcode;
   SCIP_HASHMAP* vartoexprvarmap;

   assert(scip != NULL);

   SCIP_CALL( SCIPhashmapCreate(&vartoexprvarmap, SCIPblkmem(scip), 5 * SCIPgetNVars(scip)) );

   /* if parseExpr fails, we still want to free hashmap */
   retcode = parseExpr(scip, vartoexprvarmap, exprstr, &finalpos_, expr, ownercreate, ownercreatedata);

   SCIPhashmapFree(&vartoexprvarmap);

   if( finalpos != NULL )
      *finalpos = finalpos_;

   return retcode;
}

/** captures an expression (increments usage count) */
void SCIPcaptureExpr(
   SCIP_EXPR*            expr                /**< expression to be captured */
   )
{
   SCIPexprCapture(expr);
}

/** releases an expression (decrements usage count and possibly frees expression) */
SCIP_RETCODE SCIPreleaseExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           expr                /**< pointer to expression to be released */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprRelease(scip->set, scip->stat, scip->mem->probmem, expr) );

   return SCIP_OKAY;
}

/** returns whether an expression is a variable expression */
SCIP_Bool SCIPisExprVar(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);

   return SCIPexprIsVar(scip->set, expr);
}

/** returns whether an expression is a value expression */
SCIP_Bool SCIPisExprValue(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);

   return SCIPexprIsValue(scip->set, expr);
}

/** returns whether an expression is a sum expression */
SCIP_Bool SCIPisExprSum(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);

   return SCIPexprIsSum(scip->set, expr);
}

/** returns whether an expression is a product expression */
SCIP_Bool SCIPisExprProduct(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);

   return SCIPexprIsProduct(scip->set, expr);
}

/** returns whether an expression is a power expression */
SCIP_Bool SCIPisExprPower(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);

   return SCIPexprIsPower(scip->set, expr);
}

/** print an expression as info-message */
SCIP_RETCODE SCIPprintExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be printed */
   FILE*                 file                /**< file to print to, or NULL for stdout */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprPrint(scip->set, scip->stat, scip->mem->probmem, scip->messagehdlr, file, expr) );

   return SCIP_OKAY;
}

/** initializes printing of expressions in dot format to a give FILE* pointer */
SCIP_RETCODE SCIPprintExprDotInit(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRPRINTDATA**  printdata,          /**< buffer to store dot printing data */
   FILE*                 file,               /**< file to print to, or NULL for stdout */
   SCIP_EXPRPRINT_WHAT   whattoprint         /**< info on what to print for each expression */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprPrintDotInit(scip->set, scip->stat, scip->mem->probmem, printdata, file, whattoprint) );

   return SCIP_OKAY;
}

/** initializes printing of expressions in dot format to a file with given filename */
SCIP_RETCODE SCIPprintExprDotInit2(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRPRINTDATA**  printdata,          /**< buffer to store dot printing data */
   const char*           filename,           /**< name of file to print to */
   SCIP_EXPRPRINT_WHAT   whattoprint         /**< info on what to print for each expression */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprPrintDotInit2(scip->set, scip->stat, scip->mem->probmem, printdata, filename, whattoprint) );

   return SCIP_OKAY;
}

/** main part of printing an expression in dot format */
SCIP_RETCODE SCIPprintExprDot(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRPRINTDATA*   printdata,          /**< data as initialized by \ref SCIPprintExprDotInit() */
   SCIP_EXPR*            expr                /**< expression to be printed */
   )
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprPrintDot(scip->set, scip->messagehdlr, printdata, expr) );

   return SCIP_OKAY;
}

/** finishes printing of expressions in dot format */
SCIP_RETCODE SCIPprintExprDotFinal(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRPRINTDATA**  printdata           /**< buffer where dot printing data has been stored */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprPrintDotFinal(scip->set, scip->stat, scip->mem->probmem, printdata) );

   return SCIP_OKAY;
}

/** shows a single expression by use of dot and gv
 *
 * This function is meant for debugging purposes.
 * It's signature is kept as simple as possible to make it
 * easily callable from gdb, for example.
 *
 * It prints the expression into a temporary file in dot format, then calls dot to create a postscript file,
 * then calls ghostview (gv) to show the file. SCIP will hold until ghostscript is closed.
 */
SCIP_RETCODE SCIPshowExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression to be printed */
   )
{
   /* this function is for developers, so don't bother with C variants that don't have popen() */
#if _POSIX_C_SOURCE < 2
   SCIPerrorMessage("No POSIX version 2. Try http://distrowatch.com/.");
   return SCIP_ERROR;
#else
   SCIP_EXPRPRINTDATA* dotdata;
   FILE* f;
   SCIP_RETCODE retcode = SCIP_OKAY;

   assert(scip != NULL);
   assert(expr != NULL);

   /* call dot to generate postscript output and show it via ghostview */
   f = popen("dot -Tps | gv --media=a3 -", "w");
   if( f == NULL )
   {
      SCIPerrorMessage("Calling popen() failed");
      return SCIP_FILECREATEERROR;
   }

   /* print all of the expression into the pipe */
   SCIP_CALL_TERMINATE( retcode, SCIPprintExprDotInit(scip, &dotdata, f, SCIP_EXPRPRINT_ALL), TERMINATE );
   SCIP_CALL_TERMINATE( retcode, SCIPprintExprDot(scip, dotdata, expr), TERMINATE );
   SCIP_CALL_TERMINATE( retcode, SCIPprintExprDotFinal(scip, &dotdata), TERMINATE );

 TERMINATE:
   /* close the pipe */
   (void) pclose(f);

   return retcode;
#endif
}

/** prints structure of an expression a la Maple's dismantle */
SCIP_RETCODE SCIPdismantleExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   FILE*                 file,               /**< file to print to, or NULL for stdout */
   SCIP_EXPR*            expr                /**< expression to dismantle */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprDismantle(scip->set, scip->stat, scip->mem->probmem, scip->messagehdlr, file, expr) );

   return SCIP_OKAY;
}

/** evaluate an expression in a point
 *
 * Iterates over expressions to also evaluate children, if necessary.
 * Value can be received via SCIPexprGetEvalValue().
 * If an evaluation error (division by zero, ...) occurs, this value will
 * be set to SCIP_INVALID.
 *
 * If a nonzero \p soltag is passed, then only (sub)expressions are
 * reevaluated that have a different solution tag. If a soltag of 0
 * is passed, then subexpressions are always reevaluated.
 * The tag is stored together with the value and can be received via
 * SCIPexprGetEvalTag().
 */
SCIP_RETCODE SCIPevalExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be evaluated */
   SCIP_SOL*             sol,                /**< solution to be evaluated */
   SCIP_Longint          soltag              /**< tag that uniquely identifies the solution (with its values), or 0. */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprEval(scip->set, scip->stat, scip->mem->probmem, expr, sol, soltag) );

   return SCIP_OKAY;
}

/** returns a previously unused solution tag for expression evaluation */
SCIP_EXPORT
SCIP_Longint SCIPgetExprNewSoltag(
   SCIP*                 scip                /**< SCIP data structure */
   )
{
   assert(scip != NULL);

   return ++(scip->stat->exprlastsoltag);
}

/** evaluates gradient of an expression for a given point
 *
 * Initiates an expression walk to also evaluate children, if necessary.
 * Value can be received via SCIPgetExprPartialDiffNonlinear().
 * If an error (division by zero, ...) occurs, this value will
 * be set to SCIP_INVALID.
 */
SCIP_RETCODE SCIPevalExprGradient(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be differentiated */
   SCIP_SOL*             sol,                /**< solution to be evaluated (NULL for the current LP solution) */
   SCIP_Longint          soltag              /**< tag that uniquely identifies the solution (with its values), or 0. */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprEvalGradient(scip->set, scip->stat, scip->mem->probmem, expr, sol, soltag) );

   return SCIP_OKAY;
}

/** evaluates Hessian-vector product of an expression for a given point and direction
 *
 * Evaluates children, if necessary.
 * Value can be received via SCIPgetExprPartialDiffGradientDirNonlinear().
 * If an error (division by zero, ...) occurs, this value will
 * be set to SCIP_INVALID.
 */
SCIP_RETCODE SCIPevalExprHessianDir(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be differentiated */
   SCIP_SOL*             sol,                /**< solution to be evaluated (NULL for the current LP solution) */
   SCIP_Longint          soltag,             /**< tag that uniquely identifies the solution (with its values), or 0. */
   SCIP_SOL*             direction           /**< direction */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprEvalHessianDir(scip->set, scip->stat, scip->mem->probmem, expr, sol, soltag, direction) );

   return SCIP_OKAY;
}

/** possibly reevaluates and then returns the activity of the expression
 *
 * Reevaluate activity if currently stored is no longer uptodate (some bound was changed since last evaluation).
 *
 * The owner of the expression may overwrite the methods used to evaluate the activity,
 * including whether the local or global domain of variables is used.
 * By default (no owner, or owner doesn't overwrite activity evaluation),
 * the local domain of variables is used.
 *
 * @note If expression is set to be integral, then activities are tightened to integral values.
 *   Thus, ensure that the integrality information is valid (if set to TRUE; the default (FALSE) is always ok).
 */
SCIP_RETCODE SCIPevalExprActivity(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprEvalActivity(scip->set, scip->stat, scip->mem->probmem, expr) );

   return SCIP_OKAY;
}

/** compare expressions
 * @return -1, 0 or 1 if expr1 <, =, > expr2, respectively
 * @note The given expressions are assumed to be simplified.
 */
int SCIPcompareExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr1,              /**< first expression */
   SCIP_EXPR*            expr2               /**< second expression */
   )
{
   assert(scip != NULL);

   return SCIPexprCompare(scip->set, expr1, expr2);
}

/** compute the hash value of an expression */
SCIP_RETCODE SCIPhashExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression */
   unsigned int*         hashval             /**< pointer to store the hash value */
   )
{
   SCIP_EXPRITER* it;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(expr != NULL);
   assert(hashval != NULL);

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, &it) );
   SCIP_CALL( SCIPexpriterInit(it, expr, SCIP_EXPRITER_DFS, FALSE) );
   SCIPexpriterSetStagesDFS(it, SCIP_EXPRITER_LEAVEEXPR);

   SCIP_CALL( hashExpr(scip->set, scip->mem->buffer, expr, it, NULL) );

   *hashval = SCIPexpriterGetExprUserData(it, expr).uintval;

   SCIPexpriterFree(&it);

   return SCIP_OKAY;
}

/* simplifies an expression (duplication of long doxygen comment omitted here) */
SCIP_RETCODE SCIPsimplifyExpr(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            rootexpr,           /**< expression to be simplified */
   SCIP_EXPR**           simplified,         /**< buffer to store simplified expression */
   SCIP_Bool*            changed,            /**< buffer to store if rootexpr actually changed */
   SCIP_Bool*            infeasible,         /**< buffer to store whether infeasibility has been detected */
   SCIP_DECL_EXPR_OWNERCREATE((*ownercreate)), /**< function to call to create ownerdata */
   void*                 ownercreatedata     /**< data to pass to ownercreate */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprSimplify(scip->set, scip->stat, scip->mem->probmem, rootexpr, simplified, changed, infeasible, ownercreate, ownercreatedata) );

   return SCIP_OKAY;
}

/** replaces common sub-expressions in a given expression graph by using a hash key for each expression
 *
 *  The algorithm consists of two steps:
 *
 *  1. traverse through all given expressions and compute for each of them a (not necessarily unique) hash
 *
 *  2. initialize an empty hash table and traverse through all expression; check for each of them if we can find a
 *     structural equivalent expression in the hash table; if yes we replace the expression by the expression inside the
 *     hash table, otherwise we add it to the hash table
 *
 *  @note the hash keys of the expressions are used for the hashing inside the hash table; to compute if two expressions
 *  (with the same hash) are structurally the same we use the function SCIPexprCompare().
 */
SCIP_RETCODE SCIPreplaceCommonSubexpressions(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR**           exprs,              /**< expressions (possibly replaced by equivalent on output) */
   int                   nexprs,             /**< total number of expressions */
   SCIP_Bool*            replacedroot        /**< buffer to store whether any root expression (expression in exprs) was replaced */
   )
{
   COMMONSUBEXPR_HASH_DATA hashdata;
   SCIP_EXPRITER* hashiterator;
   SCIP_EXPRITER* repliterator;
   SCIP_MULTIHASH* key2expr;
   int i;
   int nvisitedexprs = 0;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(exprs != NULL);
   assert(nexprs >= 0);
   assert(replacedroot != NULL);

   *replacedroot = FALSE;

   if( nexprs == 0 )
      return SCIP_OKAY;

   SCIP_CALL( SCIPcreateExpriter(scip, &hashiterator) );
   SCIP_CALL( SCIPexpriterInit(hashiterator, NULL, SCIP_EXPRITER_DFS, FALSE) );
   SCIPexpriterSetStagesDFS(hashiterator, SCIP_EXPRITER_LEAVEEXPR);

   /* compute all hashes for each sub-expression */
   for( i = 0; i < nexprs; ++i )
   {
      assert(exprs[i] != NULL);
      SCIP_CALL( hashExpr(scip->set, scip->mem->buffer, exprs[i], hashiterator, &nvisitedexprs) );
   }

   /* replace equivalent sub-expressions */
   hashdata.hashiterator = hashiterator;
   hashdata.set = scip->set;
   SCIP_CALL( SCIPmultihashCreate(&key2expr, scip->mem->probmem, nvisitedexprs,
         hashCommonSubexprGetKey, hashCommonSubexprEq, hashCommonSubexprKeyval, (void*)&hashdata) );

   SCIP_CALL( SCIPcreateExpriter(scip, &repliterator) );

   for( i = 0; i < nexprs; ++i )
   {
      SCIP_EXPR* newroot;
      SCIP_EXPR* newchild;
      SCIP_EXPR* child;

      /* check the root for equivalence separately first */
      SCIP_CALL( findEqualExpr(scip->set, exprs[i], key2expr, &newroot) );

      if( newroot != NULL )
      {
         assert(newroot != exprs[i]);
         assert(SCIPexprCompare(scip->set, exprs[i], newroot) == 0);

         SCIPdebugMsg(scip, "replacing common root expression of %dth expr: %p -> %p\n", i, (void*)exprs[i], (void*)newroot);

         SCIP_CALL( SCIPreleaseExpr(scip, &exprs[i]) );

         exprs[i] = newroot;
         SCIPexprCapture(newroot);

         *replacedroot = TRUE;

         continue;
      }

      /* replace equivalent sub-expressions in the tree */
      SCIP_CALL( SCIPexpriterInit(repliterator, exprs[i], SCIP_EXPRITER_DFS, FALSE) );
      SCIPexpriterSetStagesDFS(repliterator, SCIP_EXPRITER_VISITINGCHILD);

      while( !SCIPexpriterIsEnd(repliterator) )
      {
         child = SCIPexpriterGetChildExprDFS(repliterator);
         assert(child != NULL);

         /* try to find an equivalent expression */
         SCIP_CALL( findEqualExpr(scip->set, child, key2expr, &newchild) );

         /* replace child with newchild */
         if( newchild != NULL )
         {
            assert(child != newchild);
            assert(SCIPexprCompare(scip->set, child, newchild) == 0);

            SCIPdebugMsg(scip, "replacing common child expression %p -> %p\n", (void*)child, (void*)newchild);

            SCIP_CALL( SCIPreplaceExprChild(scip, SCIPexpriterGetCurrent(repliterator), SCIPexpriterGetChildIdxDFS(repliterator), newchild) );

            (void) SCIPexpriterSkipDFS(repliterator);
         }
         else
         {
            (void) SCIPexpriterGetNext(repliterator);
         }
      }
   }

   /* free memory */
   SCIPexpriterFree(&repliterator);
   SCIPmultihashFree(&key2expr);
   SCIPexpriterFree(&hashiterator);

   return SCIP_OKAY;
}

/** computes the curvature of a given expression and all its subexpressions
 *
 *  @note this function also evaluates all subexpressions w.r.t. current variable bounds
 *  @note this function relies on information from the curvature callback of expression handlers only,
 *    consider using function @ref SCIPhasExprCurvature() of the convex-nlhdlr instead, as that uses more information to deduce convexity
 */
SCIP_RETCODE SCIPcomputeExprCurvature(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   SCIP_EXPRITER* it;
   SCIP_EXPRCURV curv;
   SCIP_EXPRCURV* childcurv;
   int childcurvsize;
   SCIP_Bool success;
   SCIP_EXPRCURV trialcurv[3] = { SCIP_EXPRCURV_LINEAR, SCIP_EXPRCURV_CONVEX, SCIP_EXPRCURV_CONCAVE };
   int i, c;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(expr != NULL);

   childcurvsize = 5;
   SCIP_CALL( SCIPallocBufferArray(scip, &childcurv, childcurvsize) );

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, &it) );
   SCIP_CALL( SCIPexpriterInit(it, expr, SCIP_EXPRITER_DFS, FALSE) );
   SCIPexpriterSetStagesDFS(it, SCIP_EXPRITER_LEAVEEXPR);

   for( expr = SCIPexpriterGetCurrent(it); !SCIPexpriterIsEnd(it); expr = SCIPexpriterGetNext(it) )
   {
      curv = SCIP_EXPRCURV_UNKNOWN;

      if( !SCIPexprhdlrHasCurvature(SCIPexprGetHdlr(expr)) )
      {
         /* set curvature in expression */
         SCIPexprSetCurvature(expr, curv);
         continue;
      }

      if( SCIPexprGetNChildren(expr) > childcurvsize )
      {
         childcurvsize = SCIPcalcMemGrowSize(scip, SCIPexprGetNChildren(expr));
         SCIP_CALL( SCIPreallocBufferArray(scip, &childcurv, childcurvsize) );
      }

      for( i = 0; i < 3; ++i )
      {
         /* check if expression can have a curvature trialcurv[i] */
         SCIP_CALL( SCIPexprhdlrCurvatureExpr(SCIPexprGetHdlr(expr), scip->set, expr, trialcurv[i], &success, childcurv) );
         if( !success )
            continue;

         /* check if conditions on children are satisfied */
         for( c = 0; c < SCIPexprGetNChildren(expr); ++c )
         {
            if( (childcurv[c] & SCIPexprGetCurvature(SCIPexprGetChildren(expr)[c])) != childcurv[c] )
            {
               success = FALSE;
               break;
            }
         }

         if( success )
         {
            curv = trialcurv[i];
            break;
         }
      }

      /* set curvature in expression */
      SCIPexprSetCurvature(expr, curv);
   }

   SCIPexpriterFree(&it);

   SCIPfreeBufferArray(scip, &childcurv);

   return SCIP_OKAY;
}

/** computes integrality information of a given expression and all its subexpressions
 *
 * The integrality information can be accessed via SCIPexprIsIntegral().
 */
SCIP_RETCODE SCIPcomputeExprIntegrality(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   SCIP_EXPRITER* it;
   SCIP_Bool isintegral;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(expr != NULL);

   /* shortcut for expr without children */
   if( SCIPexprGetNChildren(expr) == 0 )
   {
      /* compute integrality information */
      SCIP_CALL( SCIPexprhdlrIntegralityExpr(SCIPexprGetHdlr(expr), scip->set, expr, &isintegral) );
      SCIPexprSetIntegrality(expr, isintegral);

      return SCIP_OKAY;
   }

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, &it) );
   SCIP_CALL( SCIPexpriterInit(it, expr, SCIP_EXPRITER_DFS, FALSE) );
   SCIPexpriterSetStagesDFS(it, SCIP_EXPRITER_LEAVEEXPR);

   for( expr = SCIPexpriterGetCurrent(it); !SCIPexpriterIsEnd(it); expr = SCIPexpriterGetNext(it) )
   {
      /* compute integrality information */
      SCIP_CALL( SCIPexprhdlrIntegralityExpr(SCIPexprGetHdlr(expr), scip->set, expr, &isintegral) );
      SCIPexprSetIntegrality(expr, isintegral);
   }

   SCIPexpriterFree(&it);

   return SCIP_OKAY;
}

/** returns the total number of variable expressions in an expression
 *
 * The function counts variable expressions in common sub-expressions only once, but
 * counts variables appearing in several variable expressions multiple times.
 */
SCIP_RETCODE SCIPgetExprNVars(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression */
   int*                  nvars               /**< buffer to store the total number of variables */
   )
{
   SCIP_EXPRITER* it;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(expr != NULL);
   assert(nvars != NULL);

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, &it) );
   SCIP_CALL( SCIPexpriterInit(it, expr, SCIP_EXPRITER_DFS, FALSE) );

   *nvars = 0;
   for( ; !SCIPexpriterIsEnd(it); expr = SCIPexpriterGetNext(it) )
      if( SCIPexprIsVar(scip->set, expr) )
         ++(*nvars);

   SCIPexpriterFree(&it);

   return SCIP_OKAY;
}

/** returns all variable expressions contained in a given expression
 *
 * The array to store all variable expressions needs to be at least of size
 * the number of unique variable expressions in the expression which is given by SCIPgetExprNVars().
 *
 * If every variable is represented by only one variable expression (common subexpression have been removed)
 * then SCIPgetExprNVars() can be bounded by SCIPgetNTotalVars().
 * If, in addition, non-active variables have been removed from the expression, e.g., by simplifying,
 * then SCIPgetExprNVars() can be bounded by SCIPgetNVars().
 *
 * @note function captures variable expressions
 */
SCIP_RETCODE SCIPgetExprVarExprs(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression */
   SCIP_EXPR**           varexprs,           /**< array to store all variable expressions */
   int*                  nvarexprs           /**< buffer to store the total number of variable expressions */
   )
{
   SCIP_EXPRITER* it;

   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(expr != NULL);
   assert(varexprs != NULL);
   assert(nvarexprs != NULL);

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, &it) );
   SCIP_CALL( SCIPexpriterInit(it, expr, SCIP_EXPRITER_DFS, FALSE) );

   *nvarexprs = 0;
   for( ; !SCIPexpriterIsEnd(it); expr = SCIPexpriterGetNext(it) )
   {
      assert(expr != NULL);

      if( SCIPexprIsVar(scip->set, expr) )
      {
         varexprs[(*nvarexprs)++] = expr;

         /* capture expression */
         SCIPcaptureExpr(expr);
      }
   }

   /* @todo sort variable expressions here? */

   SCIPexpriterFree(&it);

   return SCIP_OKAY;
}

/** calls the print callback for an expression
 *
 * @see SCIP_DECL_EXPRPRINT
 */
SCIP_EXPORT
SCIP_DECL_EXPRPRINT(SCIPcallExprPrint)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrPrintExpr(SCIPexprGetHdlr(expr), scip->set, scip->messagehdlr, expr, stage, currentchild, parentprecedence, file) );

   return SCIP_OKAY;
}

/** calls the curvature callback for an expression
 *
 * @see SCIP_DECL_EXPRCURVATURE
 *
 * Returns unknown curvature if callback not implemented.
 */
SCIP_EXPORT
SCIP_DECL_EXPRCURVATURE(SCIPcallExprCurvature)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrCurvatureExpr(SCIPexprGetHdlr(expr), scip->set, expr, exprcurvature, success, childcurv) );

   return SCIP_OKAY;
}

/** calls the monotonicity callback for an expression
 *
 * @see SCIP_DECL_EXPRMONOTONICITY
 *
 * Returns unknown monotonicity if callback not implemented.
 */
SCIP_DECL_EXPRMONOTONICITY(SCIPcallExprMonotonicity)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrMonotonicityExpr(SCIPexprGetHdlr(expr), scip->set, expr, childidx, result) );

   return SCIP_OKAY;
}

/** calls the eval callback for an expression with given values for children
 *
 * Does not iterates over expressions, but requires values for children to be given.
 * Value is not stored in expression, but returned in `val`.
 * If an evaluation error (division by zero, ...) occurs, this value will
 * be set to `SCIP_INVALID`.
 */
SCIP_RETCODE SCIPcallExprEval(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be evaluated */
   SCIP_Real*            childrenvalues,     /**< values for children */
   SCIP_Real*            val                 /**< buffer to store evaluated value */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);
   assert(childrenvalues != NULL);
   assert(val != NULL);

   SCIP_CALL( SCIPexprhdlrEvalExpr(SCIPexprGetHdlr(expr), scip->set, scip->mem->buffer, expr, val, childrenvalues, NULL) );

   return SCIP_OKAY;
}

/** calls the eval and fwdiff callback of an expression with given values for children
 *
 * Does not iterates over expressions, but requires values for children and direction to be given.
 *
 * Value is not stored in expression, but returned in `val`.
 * If an evaluation error (division by zero, ...) occurs, this value will be set to `SCIP_INVALID`.
 *
 * Direction is not stored in expression, but returned in `dot`.
 * If an differentiation error (division by zero, ...) occurs, this value will be set to `SCIP_INVALID`.
 */
SCIP_RETCODE SCIPcallExprEvalFwdiff(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression to be evaluated */
   SCIP_Real*            childrenvalues,     /**< values for children */
   SCIP_Real*            direction,          /**< direction in which to differentiate */
   SCIP_Real*            val,                /**< buffer to store evaluated value */
   SCIP_Real*            dot                 /**< buffer to store derivative value */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprhdlrEvalFwDiffExpr(SCIPexprGetHdlr(expr), scip->set, scip->mem->buffer, expr, val, dot,
         childrenvalues, NULL, direction, NULL) );

   return SCIP_OKAY;
}

/** calls the interval evaluation callback for an expression
 *
 * @see SCIP_DECL_EXPRINTEVAL
 *
 * Returns entire interval if callback not implemented.
 */
SCIP_DECL_EXPRINTEVAL(SCIPcallExprInteval)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrIntEvalExpr(SCIPexprGetHdlr(expr), scip->set, expr, interval, intevalvar, intevalvardata) );

   return SCIP_OKAY;
}

/** calls the estimate callback for an expression
 *
 * @see SCIP_DECL_EXPRESTIMATE
 *
 * Returns without success if callback not implemented.
 */
SCIP_EXPORT
SCIP_DECL_EXPRESTIMATE(SCIPcallExprEstimate)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrEstimateExpr(SCIPexprGetHdlr(expr), scip->set, expr, localbounds, globalbounds, refpoint,
         overestimate, targetvalue, coefs, constant, islocal, success, branchcand) );

   return SCIP_OKAY;
}

/** calls the initial estimators callback for an expression
 *
 * @see SCIP_DECL_EXPRINITESTIMATES
 *
 * Returns no estimators if callback not implemented.
 */
SCIP_EXPORT
SCIP_DECL_EXPRINITESTIMATES(SCIPcallExprInitestimates)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrInitEstimatesExpr(SCIPexprGetHdlr(expr), scip->set, expr, bounds, overestimate, coefs,
         constant, nreturned) );

   return SCIP_OKAY;
}

/** calls the simplify callback for an expression
 *
 * @see SCIP_DECL_EXPRSIMPLIFY
 *
 * Returns unmodified expression if simplify callback not implemented.
 *
 * Does not simplify descendants (children, etc). Use SCIPsimplifyExpr() for that.
 */
SCIP_DECL_EXPRSIMPLIFY(SCIPcallExprSimplify)
{
   assert(scip != NULL);

   /* use simplification of expression handlers */
   SCIP_CALL( SCIPexprhdlrSimplifyExpr(SCIPexprGetHdlr(expr), scip->set, expr, simplifiedexpr, ownercreate,
         ownercreatedata) );

   return SCIP_OKAY;
}

/** calls the reverse propagation callback for an expression
 *
 * @see SCIP_DECL_EXPRREVERSEPROP
 *
 * Returns unmodified childrenbounds if reverseprop callback not implemented.
 */
SCIP_EXPORT
SCIP_DECL_EXPRREVERSEPROP(SCIPcallExprReverseprop)
{
   assert(scip != NULL);

   SCIP_CALL( SCIPexprhdlrReversePropExpr(SCIPexprGetHdlr(expr), scip->set, expr, bounds, childrenbounds, infeasible) );

   return SCIP_OKAY;
}

/**@} */

/**@name Expression Iterator Methods */
/**@{ */

#ifdef NDEBUG
#undef SCIPcreateExpriter
#undef SCIPfreeExpriter
#endif

/** creates an expression iterator */
SCIP_RETCODE SCIPcreateExpriter(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPRITER**       iterator            /**< buffer to store expression iterator */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexpriterCreate(scip->stat, scip->mem->probmem, iterator) );

   return SCIP_OKAY;
}

/** frees an expression iterator */
void SCIPfreeExpriter(
   SCIP_EXPRITER**       iterator            /**< pointer to the expression iterator */
   )
{
   SCIPexpriterFree(iterator);
}

/**@} */


/**@name Quadratic expression functions */
/**@{ */

#ifdef NDEBUG
#undef SCIPcheckExprQuadratic
#undef SCIPfreeExprQuadratic
#undef SCIPcomputeExprQuadraticCurvature
#endif

/** checks whether an expression is quadratic
 *
 * An expression is quadratic if it is either a square (of some expression), a product (of two expressions),
 * or a sum of terms where at least one is a square or a product.
 *
 * Use SCIPexprGetQuadraticData() to get data about the representation as quadratic.
 */
SCIP_RETCODE SCIPcheckExprQuadratic(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< expression */
   SCIP_Bool*            isquadratic         /**< buffer to store result */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprCheckQuadratic(scip->set, scip->mem->probmem, expr, isquadratic) );

   return SCIP_OKAY;
}

/** frees information on quadratic representation of an expression
 *
 * Before doing changes to an expression, it can be useful to call this function.
 */
void SCIPfreeExprQuadratic(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< expression */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIPexprFreeQuadratic(scip->mem->probmem, expr);
}

/** evaluates quadratic term in a solution
 *
 * \note This requires that every expression used in the quadratic data is a variable expression.
 */
SCIP_Real SCIPevalExprQuadratic(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< quadratic expression */
   SCIP_SOL*             sol                 /**< solution to evaluate, or NULL for LP solution */
   )
{
   SCIP_Real auxvalue;
   int nlinexprs;
   SCIP_Real* lincoefs;
   SCIP_EXPR** linexprs;
   int nquadexprs;
   int nbilinexprs;
   int i;

   assert(scip != NULL);
   assert(expr != NULL);

   SCIPexprGetQuadraticData(expr, &auxvalue, &nlinexprs, &linexprs, &lincoefs, &nquadexprs, &nbilinexprs, NULL, NULL);

   /* linear terms */
   for( i = 0; i < nlinexprs; ++i )
   {
      assert(SCIPexprIsVar(scip->set, linexprs[i]));
      auxvalue += lincoefs[i] * SCIPgetSolVal(scip, sol, SCIPgetVarExprVar(linexprs[i]));
   }

   /* quadratic terms */
   for( i = 0; i < nquadexprs; ++i )
   {
      SCIP_EXPR* quadexprterm;
      SCIP_Real lincoef;
      SCIP_Real sqrcoef;
      SCIP_Real solval;

      SCIPexprGetQuadraticQuadTerm(expr, i, &quadexprterm, &lincoef, &sqrcoef, NULL, NULL, NULL);

      assert(SCIPexprIsVar(scip->set, quadexprterm));

      solval = SCIPgetSolVal(scip, sol, SCIPgetVarExprVar(quadexprterm));
      auxvalue += (lincoef + sqrcoef * solval) * solval;
   }

   /* bilinear terms */
   for( i = 0; i < nbilinexprs; ++i )
   {
      SCIP_EXPR* expr1;
      SCIP_EXPR* expr2;
      SCIP_Real coef;

      SCIPexprGetQuadraticBilinTerm(expr, i, &expr1, &expr2, &coef, NULL, NULL);

      assert(SCIPexprIsVar(scip->set, expr1));
      assert(SCIPexprIsVar(scip->set, expr2));
      auxvalue += coef * SCIPgetSolVal(scip, sol, SCIPgetVarExprVar(expr1)) * SCIPgetSolVal(scip, sol, SCIPgetVarExprVar(expr2));
   }

   return auxvalue;
}

/** prints quadratic expression */
SCIP_RETCODE SCIPprintExprQuadratic(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr                /**< quadratic expression */
   )
{
   SCIP_Real constant;
   int nlinexprs;
   SCIP_Real* lincoefs;
   SCIP_EXPR** linexprs;
   int nquadexprs;
   int nbilinexprs;
   int c;

   assert(scip != NULL);
   assert(expr != NULL);

   SCIPexprGetQuadraticData(expr, &constant, &nlinexprs, &linexprs, &lincoefs, &nquadexprs, &nbilinexprs, NULL, NULL);

   SCIPinfoMessage(scip, NULL, "Constant: %g\n", constant);

   SCIPinfoMessage(scip, NULL, "Linear: ");
   for( c = 0; c < nlinexprs; ++c )
   {
      SCIPinfoMessage(scip, NULL, "%g * ", lincoefs[c]);
      SCIP_CALL( SCIPprintExpr(scip, linexprs[c], NULL) );
      if( c < nlinexprs - 1 )
         SCIPinfoMessage(scip, NULL, " + ");
   }
   SCIPinfoMessage(scip, NULL, "\n");

   SCIPinfoMessage(scip, NULL, "Quadratic: ");
   for( c = 0; c < nquadexprs; ++c )
   {
      SCIP_EXPR* quadexprterm;
      SCIP_Real lincoef;
      SCIP_Real sqrcoef;

      SCIPexprGetQuadraticQuadTerm(expr, c, &quadexprterm, &lincoef, &sqrcoef, NULL, NULL, NULL);
      SCIPinfoMessage(scip, NULL, "(%g * sqr(", sqrcoef);
      SCIP_CALL( SCIPprintExpr(scip, quadexprterm, NULL) );
      SCIPinfoMessage(scip, NULL, ") + %g) * ", lincoef);
      SCIP_CALL( SCIPprintExpr(scip, quadexprterm, NULL) );
      if( c < nquadexprs - 1 )
         SCIPinfoMessage(scip, NULL, " + ");
   }
   SCIPinfoMessage(scip, NULL, "\n");

   if( nbilinexprs == 0 )
   {
      SCIPinfoMessage(scip, NULL, "Bilinear: none\n");
      return SCIP_OKAY;
   }

   SCIPinfoMessage(scip, NULL, "Bilinear: ");
   for( c = 0; c < nbilinexprs; ++c )
   {
      SCIP_EXPR* expr1;
      SCIP_EXPR* expr2;
      SCIP_Real coef;

      SCIPexprGetQuadraticBilinTerm(expr, c, &expr1, &expr2, &coef, NULL, NULL);

      SCIPinfoMessage(scip, NULL, "%g * ", coef);
      SCIP_CALL( SCIPprintExpr(scip, expr1, NULL) );
      SCIPinfoMessage(scip, NULL, " * ");
      SCIP_CALL( SCIPprintExpr(scip, expr2, NULL) );
      if( c < nbilinexprs - 1 )
         SCIPinfoMessage(scip, NULL, " + ");
   }
   SCIPinfoMessage(scip, NULL, "\n");

   SCIPinfoMessage(scip, NULL, "Bilinear of quadratics: \n");
   for( c = 0; c < nquadexprs; ++c )
   {
      SCIP_EXPR* quadexprterm;
      int nadjbilin;
      int* adjbilin;
      int i;

      SCIPexprGetQuadraticQuadTerm(expr, c, &quadexprterm, NULL, NULL, &nadjbilin, &adjbilin, NULL);

      SCIPinfoMessage(scip, NULL, "  For ");
      SCIP_CALL( SCIPprintExpr(scip, quadexprterm, NULL) );
      SCIPinfoMessage(scip, NULL, " we see: ");
      for( i = 0; i < nadjbilin; ++i )
      {
         SCIP_EXPR* expr1;
         SCIP_EXPR* expr2;
         SCIP_Real coef;

         SCIPexprGetQuadraticBilinTerm(expr, adjbilin[i], &expr1, &expr2, &coef, NULL, NULL);

         SCIPinfoMessage(scip, NULL, "%g * ", coef);
         SCIP_CALL( SCIPprintExpr(scip, expr1, NULL) );
         SCIPinfoMessage(scip, NULL, " * ");
         SCIP_CALL( SCIPprintExpr(scip, expr2, NULL) );
         if( i < nadjbilin - 1 )
            SCIPinfoMessage(scip, NULL, " + ");
      }
      SCIPinfoMessage(scip, NULL, "\n");
   }

   return SCIP_OKAY;
}

/** checks the curvature of the quadratic expression
 *
 * For this, it builds the matrix Q of quadratic coefficients and computes its eigenvalues using LAPACK.
 * If Q is
 * - semidefinite positive -> curv is set to convex,
 * - semidefinite negative -> curv is set to concave,
 * - otherwise -> curv is set to unknown.
 *
 * If `assumevarfixed` is given and some expressions in quadratic terms correspond to variables present in
 * this hashmap, then the corresponding rows and columns are ignored in the matrix Q.
 */
SCIP_RETCODE SCIPcomputeExprQuadraticCurvature(
   SCIP*                 scip,               /**< SCIP data structure */
   SCIP_EXPR*            expr,               /**< quadratic expression */
   SCIP_EXPRCURV*        curv,               /**< pointer to store the curvature of quadratics */
   SCIP_HASHMAP*         assumevarfixed,     /**< hashmap containing variables that should be assumed to be fixed, or NULL */
   SCIP_Bool             storeeigeninfo      /**< whether the eigenvalues and eigenvectors should be stored */
   )
{
   assert(scip != NULL);
   assert(scip->mem != NULL);

   SCIP_CALL( SCIPexprComputeQuadraticCurvature(scip->set, scip->mem->probmem, scip->mem->buffer, scip->messagehdlr,
         expr, curv, assumevarfixed, storeeigeninfo) );

   return SCIP_OKAY;
}

/**@} */