analysis.c

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      theConstraints = GetConstraintRecord(theEnv);
      thePattern->constraints = theConstraints;
      thePattern->constraints->anyAllowed = FALSE;
      thePattern->constraints->instanceAddressesAllowed = TRUE;
      thePattern->constraints->factAddressesAllowed = TRUE;
      thePattern->derivedConstraints = TRUE;
     }

   /*===================================================*/
   /* Otherwise a pattern variable is being propagated. */
   /*===================================================*/

   else
     {
      theType = thePattern->type;
      theVariable = (struct symbolHashNode *) thePattern->value;
     }

   /*===================================================*/
   /* Propagate the variable location to any additional */
   /* fields associated with the binding variable.      */
   /*===================================================*/

   if (thePattern->type != PATTERN_CE)
     {
      PropagateVariableToNodes(theEnv,thePattern->bottom,theType,theVariable,
                               thePattern,patternHead->beginNandDepth,
                               TRUE,FALSE);

      if (ProcessField(theEnv,thePattern,multifieldHeader,patternHead))
        { return(TRUE); }
     }

   /*=================================================================*/
   /* Propagate the constraints to other fields, slots, and patterns. */
   /*=================================================================*/

   return(PropagateVariableDriver(theEnv,patternHead,thePattern,multifieldHeader,theType,
                                  theVariable,thePattern,TRUE));
  }

/*******************************************/
/* PropagateVariableDriver: Driver routine */
/*   for propagating variable references.  */
/*******************************************/
static int PropagateVariableDriver(
  void *theEnv,
  struct lhsParseNode *patternHead,
  struct lhsParseNode *theNode,
  struct lhsParseNode *multifieldHeader,
  int theType,
  struct symbolHashNode *variableName,
  struct lhsParseNode *theReference,
  int assignReference)
  {
   /*===================================================*/
   /* Propagate the variable location to any additional */
   /* constraints associated with the binding variable. */
   /*===================================================*/

   if (multifieldHeader != NULL)
     {
      if (PropagateVariableToNodes(theEnv,multifieldHeader->right,theType,variableName,
                                   theReference,patternHead->beginNandDepth,assignReference,FALSE))
        {
         VariableMixingErrorMessage(theEnv,variableName);
         return(TRUE);
        }
     }

   /*========================================================*/
   /* Propagate the variable location to fields/slots in the */
   /* same pattern which appear after the binding variable.  */
   /*========================================================*/

   if (PropagateVariableToNodes(theEnv,theNode->right,theType,variableName,theReference,
                                patternHead->beginNandDepth,assignReference,FALSE))
     {
      VariableMixingErrorMessage(theEnv,variableName);
      return(TRUE);
     }

   /*======================================================*/
   /* Propagate values to other patterns if the pattern in */
   /* which the variable is found is not a "not" CE or the */
   /* last pattern within a nand CE.                       */
   /*======================================================*/

   if (((patternHead->type == PATTERN_CE) || (patternHead->type == TEST_CE)) &&
       (patternHead->negated == FALSE) &&
       (patternHead->beginNandDepth <= patternHead->endNandDepth))
     {
      int ignoreVariableMixing;

      /*============================================================*/
      /* If the variables are propagated from a test CE, then don't */
      /* check for mixing of single and multifield variables (since */
      /* previously bound multifield variables typically have the $ */
      /* removed when passed as an argument to a function unless    */
      /* sequence expansion is desired).                            */
      /*============================================================*/

      if (patternHead->type == TEST_CE) ignoreVariableMixing = TRUE;
      else ignoreVariableMixing = FALSE;

      /*==========================*/
      /* Propagate the reference. */
      /*==========================*/

      if (PropagateVariableToNodes(theEnv,patternHead->bottom,theType,variableName,theReference,
                                   patternHead->beginNandDepth,assignReference,
                                   ignoreVariableMixing))
       {
         VariableMixingErrorMessage(theEnv,variableName);
         return(TRUE);
        }
     }

   /*==============================================*/
   /* Return FALSE to indicate that no errors were */
   /* generated by the variable propagation.       */
   /*==============================================*/

   return(FALSE);
  }

/********************************************************/
/* ProcessField: Processes a field or slot of a pattern */
/*   which does not contain a binding variable.         */
/********************************************************/
static int ProcessField(
  void *theEnv,
  struct lhsParseNode *thePattern,
  struct lhsParseNode *multifieldHeader,
  struct lhsParseNode *patternHead)
  {
   struct lhsParseNode *theList, *tempList;

   /*====================================================*/
   /* Nothing needs to be done for the node representing */
   /* the entire pattern. Return FALSE to indicate that  */
   /* no errors were generated.                          */
   /*====================================================*/

   if (thePattern->type == PATTERN_CE) return(FALSE);

   /*====================================================================*/
   /* Derive a set of constraints based on values found in the slot or   */
   /* field. For example, if a slot can only contain the values 1, 2, or */
   /* 3, the field constraint ~2 would generate a constraint record that */
   /* only allows the value 1 or 3. Once generated, the constraints are  */
   /* propagated to other slots and fields.                              */
   /*====================================================================*/

   theList = DeriveVariableConstraints(theEnv,thePattern);
   for (tempList = theList; tempList != NULL; tempList = tempList->right)
     {
      if (PropagateVariableDriver(theEnv,patternHead,thePattern,multifieldHeader,tempList->type,
                                  (SYMBOL_HN *) tempList->value,tempList,FALSE))
        {
         ReturnLHSParseNodes(theEnv,theList);
         return(TRUE);
        }
     }
   ReturnLHSParseNodes(theEnv,theList);

   /*===========================================================*/
   /* Check for "variable referenced, but not previously bound" */
   /* errors. Return TRUE if this type of error is detected.    */
   /*===========================================================*/

   if (UnboundVariablesInPattern(theEnv,thePattern,(int) patternHead->whichCE))
     { return(TRUE); }

   /*==================================================*/
   /* Check for constraint errors for this slot/field. */
   /* If the slot/field has unmatchable constraints    */
   /* then return TRUE to indicate a semantic error.   */
   /*==================================================*/

   if (ProcessConnectedConstraints(theEnv,thePattern,multifieldHeader,patternHead))
     { return(TRUE); }

   /*==============================================================*/
   /* Convert the slot/field constraint to a series of expressions */
   /* that will be used in the pattern and join networks.          */
   /*==============================================================*/

   FieldConversion(theEnv,thePattern,patternHead);

   /*=========================================================*/
   /* Return FALSE to indicate that no errors were generated. */
   /*=========================================================*/

   return(FALSE);
  }

/*************************************************************/
/* PropagateVariableToNodes: Propagates variable references  */
/*  to all other variables within the semantic scope of the  */
/*  bound variable. That is, a variable reference cannot be  */
/*  beyond an enclosing not/and CE combination. The          */
/*  restriction of propagating variables beyond an enclosing */
/*  not CE is handled within the GetVariables function.      */
/*************************************************************/
static int PropagateVariableToNodes(
  void *theEnv,
  struct lhsParseNode *theNode,
  int theType,
  struct symbolHashNode *variableName,
  struct lhsParseNode *theReference,
  int startDepth,
  int assignReference,
  int ignoreVariableTypes)
  {
   struct constraintRecord *tempConstraints;

   /*===========================================*/
   /* Traverse the nodes using the bottom link. */
   /*===========================================*/

   while (theNode != NULL)
     {
      /*==================================================*/
      /* If the field/slot contains a predicate or return */
      /* value constraint, then propagate the variable to */
      /* the expression associated with that constraint.  */
      /*==================================================*/

      if (theNode->expression != NULL)
        {
         PropagateVariableToNodes(theEnv,theNode->expression,theType,variableName,
                                  theReference,startDepth,assignReference,TRUE);
        }

      /*======================================================*/
      /* If the field/slot is a single or multifield variable */
      /* with the same name as the propagated variable,       */
      /* then propagate the variable location to this node.   */
      /*======================================================*/

      else if (((theNode->type == SF_VARIABLE) || (theNode->type == MF_VARIABLE)) &&
               (theNode->value == (void *) variableName))
        {
         /*======================================================*/
         /* Check for mixing of single and multifield variables. */
         /*======================================================*/

         if (ignoreVariableTypes == FALSE)
           {
            if (((theType == SF_VARIABLE) && (theNode->type == MF_VARIABLE)) ||
                ((theType == MF_VARIABLE) && (theNode->type == SF_VARIABLE)))
              { return(TRUE); }
           }

         /*======================================================*/
         /* Intersect the propagated variable's constraints with */
         /* the current constraints for this field/slot.         */
         /*======================================================*/

         if ((theReference->constraints != NULL) && (! theNode->negated))
           {
            tempConstraints = theNode->constraints;
            theNode->constraints = IntersectConstraints(theEnv,theReference->constraints,
                                                        tempConstraints);
            if (theNode->derivedConstraints)
              { RemoveConstraint(theEnv,tempConstraints); }

            theNode->derivedConstraints = TRUE;
           }


         /*=====================================================*/
         /* Don't propagate the variable if it originates from  */
         /* a different type of pattern object and the variable */
         /* reference has already been resolved.                */
         /*=====================================================*/

         if (assignReference)
           {
            if (theNode->referringNode == NULL)
              { theNode->referringNode = theReference; }
            else if (theReference->pattern == theNode->pattern)
              { theNode->referringNode = theReference; }
            else if (theReference->patternType == theNode->patternType)
              { theNode->referringNode = theReference; }
           }
        }

      /*========================================================*/
      /* If the field/slot is the node representing the entire  */
      /* pattern, then propagate the variable location to the   */
      /* fact address associated with the pattern (if it is the */
      /* same variable name).                                   */
      /*========================================================*/

      else if ((theNode->type == PATTERN_CE) &&
               (theNode->value == (void *) variableName) &&
               (assignReference == TRUE))
        {
         if (theType == MF_VARIABLE) return(TRUE);

         theNode->referringNode = theReference;
        }

      /*=====================================================*/
      /* Propagate the variable to other fields contained    */
      /* within the same & field constraint or same pattern. */
      /*=====================================================*/

      if (theNode->right != NULL)
        {
         if (PropagateVariableToNodes(theEnv,theNode->right,theType,variableName,
                                      theReference,startDepth,assignReference,ignoreVariableTypes))
           { return(TRUE); }
        }

      /*============================================================*/
      /* Propagate the variable to other patterns within the same   */
      /* semantic scope (if dealing with the node for an entire     */
      /* pattern) or to the next | field constraint within a field. */
      /*============================================================*/

      if ((theNode->type == PATTERN_CE) || (theNode->type == TEST_CE))
        {
         if (theNode->endNandDepth < startDepth) theNode = NULL;
         else theNode = theNode->bottom;
        }
      else
        { theNode = theNode->bottom; }
     }