754 lines
14 KiB
C
754 lines
14 KiB
C
/**
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* @file terms.c
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* \brief Term related base functions.
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*
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* Intended to be a standalone file, however during development it turned out that a termlist structure was needed
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* to define term types, so there is now a dependency loop with termlists.c.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <limits.h>
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#include "terms.h"
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#include "debug.h"
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#include "memory.h"
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#include "ctype.h"
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/* external definitions */
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extern Term TERM_Function;
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extern int inTermlist (); // suppresses a warning, but at what cost?
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extern int globalLatex;
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/* forward declarations */
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void indent (void);
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/* useful macros */
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#define RID_UNDEF MIN_INT
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/* main code */
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/* Two types of terms: general, and normalized. Normalized rewrites all
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tuples to (x,(y,z))..NULL form, making list traversal easy. */
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//! Initialization of terms code.
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void
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termsInit (void)
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{
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return;
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}
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//! Cleanup of terms code.
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void
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termsDone (void)
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{
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return;
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}
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//! Allocate memory for a term.
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/**
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*@return A pointer to the new term memory, which is not yet initialised.
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*/
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Term
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makeTerm ()
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{
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return (Term) memAlloc (sizeof (struct term));
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}
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//! Create a fresh encrypted term from two existing terms.
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/**
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*@return A pointer to the new term.
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*/
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Term
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makeTermEncrypt (Term t1, Term t2)
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{
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Term term = makeTerm ();
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term->type = ENCRYPT;
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term->stype = NULL;
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term->op = t1;
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term->key = t2;
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return term;
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}
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//! Create a fresh term tuple from two existing terms.
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/**
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*@return A pointer to the new term.
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*/
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Term
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makeTermTuple (Term t1, Term t2)
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{
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if (t1 == NULL)
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{
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if (t2 == NULL)
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{
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#ifdef DEBUG
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debug (5, "Trying to make a tuple node with an empty term.");
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#endif
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return NULL;
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}
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else
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return t2;
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}
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if (t2 == NULL)
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{
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return t1;
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}
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Term tt = makeTerm ();
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tt->type = TUPLE;
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tt->stype = NULL;
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tt->op1 = t1;
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tt->op2 = t2;
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return tt;
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}
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//! Make a term of the given type with run identifier and symbol.
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/**
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*@return A pointer to the new term.
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*\sa GLOBAL, VARIABLE, LEAF, ENCRYPT, TUPLE
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*/
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Term
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makeTermType (const int type, const Symbol symb, const int runid)
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{
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Term term = makeTerm ();
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term->type = type;
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term->stype = NULL;
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term->subst = NULL;
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term->symb = symb;
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term->runid = runid;
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return term;
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}
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//! Unwrap any substitutions.
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/**
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* For speed, it is also a macro. Sometimes it will call
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* deVarScan to do the actual unwinding.
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*@return A term that is either not a variable, or has a NULL substitution.
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*\sa deVar()
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*/
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Term
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deVarScan (Term t)
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{
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while (realTermVariable (t) && t->subst != NULL)
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t = t->subst;
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return t;
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}
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//! Determine whether a term contains an unsubstituted variable as subterm.
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/**
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*@return True iff there is an open variable as subterm.
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*/
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int
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hasTermVariable (Term term)
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{
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if (term == NULL)
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return 0;
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term = deVar (term);
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if (realTermLeaf (term))
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return realTermVariable (term);
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else
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{
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if (realTermTuple (term))
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return (hasTermVariable (term->op1) || hasTermVariable (term->op2));
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else
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return (hasTermVariable (term->op) || hasTermVariable (term->key));
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}
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}
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//!Tests whether two terms are completely identical.
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/**
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* This also includes
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* variables. This is the recursive function.
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* We assume the term is normalized, e.g. no tupling has direct
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* subtupling.
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*@return True iff the terms are equal.
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*\sa isTermEqual()
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*/
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int
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isTermEqualFn (Term term1, Term term2)
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{
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term1 = deVar (term1);
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term2 = deVar (term2);
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if (term1 == term2)
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return 1;
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if ((term1 == NULL) || (term2 == NULL))
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return 0;
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if (term1->type != term2->type)
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{
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return 0;
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}
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if (realTermLeaf (term1))
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{
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return (term1->symb == term2->symb && term1->runid == term2->runid);
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}
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else
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{
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/* ENCRYPT or TUPLE */
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if (realTermEncrypt (term1))
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{
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/* for optimization of encryption equality, we compare
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operator 2 first (we expect it to be a smaller term)
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*/
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return (isTermEqualFn (term1->key, term2->key) &&
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isTermEqualFn (term1->op, term2->op));
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}
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else
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{
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/* tuple */
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return (isTermEqualFn (term1->op1, term2->op1) &&
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isTermEqualFn (term1->op2, term2->op2));
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}
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}
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}
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//! See if a term is a subterm of another.
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/**
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*@param t Term to be checked for a subterm.
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*@param tsub Subterm.
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*@return True iff tsub is a subterm of t.
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*/
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int
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termOccurs (Term t, Term tsub)
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{
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t = deVar (t);
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tsub = deVar (tsub);
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if (isTermEqual (t, tsub))
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return 1;
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if (realTermLeaf (t))
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return 0;
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if (realTermTuple (t))
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return (termOccurs (t->op1, tsub) || termOccurs (t->op2, tsub));
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else
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return (termOccurs (t->op, tsub) || termOccurs (t->key, tsub));
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}
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//! Print a term to stdout.
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/**
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* The tuple printing only works correctly for normalized terms.
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* If not, they might are displayed as "((x,y),z)". Maybe that is even
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* desirable to distinguish them.
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*\sa termTuplePrint()
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*/
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void
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termPrint (Term term)
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{
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if (term == NULL)
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{
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printf ("Empty term");
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return;
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}
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#ifdef DEBUG
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if (!DEBUGL (1))
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{
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term = deVar (term);
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}
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#else
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term = deVar (term);
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#endif
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if (realTermLeaf (term))
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{
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symbolPrint (term->symb);
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if (realTermVariable (term))
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printf ("V");
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if (term->runid >= 0)
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{
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if (globalLatex)
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printf ("\\sharp%i", term->runid);
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else
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printf ("#%i", term->runid);
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}
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if (term->subst != NULL)
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{
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if (globalLatex)
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printf ("\\rightarrow");
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else
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printf ("->");
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termPrint (term->subst);
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}
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}
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if (realTermTuple (term))
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{
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printf ("(");
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termTuplePrint(term);
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printf (")");
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return;
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}
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if (realTermEncrypt (term))
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{
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if (isTermLeaf (term->key)
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&& inTermlist (term->key->stype, TERM_Function))
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{
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/* function application */
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termPrint (term->key);
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printf ("(");
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termTuplePrint (term->op);
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printf (")");
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}
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else
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{
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/* normal encryption */
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if (globalLatex)
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{
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printf ("\\{");
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termTuplePrint (term->op);
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printf ("\\}_{");
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termPrint (term->key);
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printf ("}");
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}
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else
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{
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printf ("{");
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termTuplePrint (term->op);
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printf ("}");
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termPrint (term->key);
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}
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}
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}
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}
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//! Print an inner (tuple) term to stdout, without brackets.
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/**
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* The tuple printing only works correctly for normalized terms.
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* If not, they might are displayed as "((x,y),z)". Maybe that is even
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* desirable to distinguish them.
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*/
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void
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termTuplePrint (Term term)
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{
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if (term == NULL)
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{
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printf ("Empty term");
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return;
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}
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term = deVar(term);
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while (realTermTuple (term))
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{
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// To remove any brackets, change this into termTuplePrint.
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termPrint (term->op1);
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printf (",");
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term = deVar(term->op2);
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}
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termPrint(term);
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return;
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}
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//! Make a deep copy of a term.
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/**
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* Leaves are not copied.
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*@return If the original was a leaf, then the pointer is simply returned. Otherwise, new memory is allocated and the node is copied recursively.
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*\sa termDuplicateDeep()
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*/
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Term
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termDuplicate (const Term term)
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{
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Term newterm;
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if (term == NULL)
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return NULL;
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if (realTermLeaf (term))
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return term;
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newterm = (Term) memAlloc (sizeof (struct term));
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newterm->type = term->type;
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if (realTermEncrypt (term))
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{
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newterm->op = termDuplicate (term->op);
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newterm->key = termDuplicate (term->key);
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}
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else
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{
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newterm->op1 = termDuplicate (term->op1);
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newterm->op2 = termDuplicate (term->op2);
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}
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return newterm;
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}
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//! Make a true deep copy of a term.
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/**
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* Currently, it this function is not to be used, so we can be sure leaf nodes occur only once in the system.
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*@return New memory is allocated and the node is copied recursively.
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*\sa termDuplicate()
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*/
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Term
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termDuplicateDeep (const Term term)
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{
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Term newterm;
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if (term == NULL)
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return NULL;
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newterm = (Term) memAlloc (sizeof (struct term));
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if (realTermLeaf (term))
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{
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memcpy (newterm, term, sizeof (struct term));
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}
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else
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{
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newterm->type = term->type;
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if (realTermEncrypt (term))
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{
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newterm->op = termDuplicateDeep (term->op);
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newterm->key = termDuplicateDeep (term->key);
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}
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else
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{
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newterm->op1 = termDuplicateDeep (term->op1);
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newterm->op2 = termDuplicateDeep (term->op2);
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}
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}
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return newterm;
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}
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//! Make a copy of a term, but remove substituted variable nodes.
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/**
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* Remove all instantiated variables on the way down.
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*\sa termDuplicate()
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*/
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Term
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termDuplicateUV (Term term)
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{
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Term newterm;
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if (term == NULL)
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return NULL;
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term = deVar (term);
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if (realTermLeaf (term))
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return term;
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newterm = (Term) memAlloc (sizeof (struct term));
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newterm->type = term->type;
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if (realTermEncrypt (term))
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{
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newterm->op = termDuplicateUV (term->op);
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newterm->key = termDuplicateUV (term->key);
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}
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else
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{
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newterm->op1 = termDuplicateUV (term->op1);
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newterm->op2 = termDuplicateUV (term->op2);
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}
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return newterm;
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}
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/*
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realTermDuplicate
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make a deep copy of a term, also of leaves.
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*/
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Term
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realTermDuplicate (const Term term)
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{
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Term newterm;
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if (term == NULL)
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return NULL;
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newterm = (Term) memAlloc (sizeof (struct term));
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if (realTermLeaf (term))
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{
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memcpy (newterm, term, sizeof (struct term));
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}
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else
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{
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newterm->type = term->type;
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if (realTermEncrypt (term))
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{
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newterm->op = realTermDuplicate (term->op);
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newterm->key = realTermDuplicate (term->key);
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}
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else
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{
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newterm->op1 = realTermDuplicate (term->op1);
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newterm->op2 = realTermDuplicate (term->op2);
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}
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}
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return newterm;
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}
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//!Removes a term and deallocates memory.
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/**
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* Is meant to remove terms make with termDuplicate. Only deallocates memory
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* of nodes, not of leaves.
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*\sa termDuplicate(), termDuplicateUV()
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*/
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void
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termDelete (const Term term)
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{
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if (term != NULL && !realTermLeaf (term))
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{
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if (realTermEncrypt (term))
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{
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termDelete (term->op);
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termDelete (term->key);
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}
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else
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{
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termDelete (term->op1);
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termDelete (term->op2);
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}
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memFree (term, sizeof (struct term));
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}
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}
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//! Normalize a term with respect to tupling.
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/**
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* Avoids problems with associativity by rewriting every ((x,y),z) to
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* (x,(y,z)), i.e. a normal form for terms, after which equality is
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* okay. No memory was allocated or deallocated, as only pointers are swapped.
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*
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*@return After execution, the term pointed at has been normalized. */
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void
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termNormalize (Term term)
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{
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term = deVar (term);
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if (term == NULL || realTermLeaf (term))
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return;
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if (realTermEncrypt (term))
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{
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termNormalize (term->op);
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termNormalize (term->key);
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}
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else
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{
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/* normalize left hand first,both for tupling and for
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encryption */
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termNormalize (term->op1);
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/* check for ((x,y),z) construct */
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if (realTermTuple (term->op1))
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{
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/* temporarily store the old terms */
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Term tx = (term->op1)->op1;
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Term ty = (term->op1)->op2;
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Term tz = term->op2;
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/* move node */
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term->op2 = term->op1;
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/* construct (x,(y,z)) version */
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term->op1 = tx;
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(term->op2)->op1 = ty;
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(term->op2)->op2 = tz;
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}
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termNormalize (term->op2);
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}
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}
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//! Copy a term, and ensure all run identifiers are set to the new value.
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/**
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* Strange code. Only to be used on locals, as is stupidly replaces all run identifiers.
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*@return The new term.
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*\sa termDuplicate()
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*/
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Term
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termRunid (Term term, int runid)
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{
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if (term == NULL)
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return NULL;
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if (realTermLeaf (term))
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{
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/* leaf */
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if (term->runid == runid)
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return term;
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else
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{
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Term newt = termDuplicate (term);
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newt->runid = runid;
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return newt;
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}
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}
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else
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{
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/* anything else, recurse */
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if (realTermEncrypt (term))
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{
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return makeTermEncrypt (termRunid (term->op, runid),
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termRunid (term->key, runid));
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}
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else
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{
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return makeTermTuple (termRunid (term->op1, runid),
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termRunid (term->op2, runid));
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}
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}
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}
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//! Determine tuple width of a given term.
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/**
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*\sa tupleProject()
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*/
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int
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tupleCount (Term tt)
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{
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if (tt == NULL)
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{
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return 0;
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}
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else
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{
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deVar (tt);
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if (!realTermTuple (tt))
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{
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return 1;
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}
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else
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{
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return (tupleCount (tt->op1) + tupleCount (tt->op2));
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}
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}
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}
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//! Yield the projection Pi(n) of a term.
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/**
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*@param tt Term
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*@param n The index in the tuple.
|
|
*@return Returns either a pointer to a term, or NULL if the index is out of range.
|
|
*\sa tupleCount()
|
|
*/
|
|
Term
|
|
tupleProject (Term tt, int n)
|
|
{
|
|
if (tt == NULL)
|
|
{
|
|
return NULL;
|
|
}
|
|
deVar (tt);
|
|
if (!realTermTuple (tt))
|
|
{
|
|
if (n > 0)
|
|
{
|
|
/* no tuple, adressing error */
|
|
return NULL;
|
|
}
|
|
else
|
|
{
|
|
/* no tuple */
|
|
return tt;
|
|
}
|
|
}
|
|
else
|
|
{
|
|
/* there is a tuple to traverse */
|
|
int left = tupleCount (tt->op1);
|
|
if (n >= left)
|
|
{
|
|
/* it's in the right hand side */
|
|
return tupleProject (tt->op2, n - left);
|
|
}
|
|
else
|
|
{
|
|
/* left hand side */
|
|
return tupleProject (tt->op1, n);
|
|
}
|
|
}
|
|
}
|
|
|
|
//! Determine size of term.
|
|
/**
|
|
* Determines the size of a term according to some heuristic.
|
|
* Currently, the encryption operator is weighed as well.
|
|
*@return Returns a nonnegative integer.
|
|
*\sa termDistance()
|
|
*/
|
|
|
|
int
|
|
termSize(Term t)
|
|
{
|
|
if (t == NULL)
|
|
{
|
|
return 0;
|
|
}
|
|
|
|
t = deVar(t);
|
|
if (realTermLeaf(t))
|
|
{
|
|
return 1;
|
|
}
|
|
else
|
|
{
|
|
if (realTermEncrypt(t))
|
|
{
|
|
return 1 + termSize(t->op) + termSize(t->key);
|
|
}
|
|
else
|
|
{
|
|
return termSize(t->op1) + termSize(t->op2);
|
|
}
|
|
}
|
|
}
|
|
|
|
//! Determine distance between two terms.
|
|
/**
|
|
*@return A float value between 0, completely dissimilar, and 1, equal.
|
|
*\sa termSize()
|
|
*/
|
|
|
|
float
|
|
termDistance(Term t1, Term t2)
|
|
{
|
|
/* First the special cases: no equal subterms, completely equal */
|
|
if (isTermEqual(t1,t2))
|
|
return 1;
|
|
|
|
t1 = deVar(t1);
|
|
t2 = deVar(t2);
|
|
|
|
int t1s = termSize(t1);
|
|
int t2s = termSize(t2);
|
|
|
|
if (t1 == NULL || t2 == NULL)
|
|
{
|
|
return 0;
|
|
}
|
|
if (t1->type != t2->type)
|
|
{
|
|
/* unequal type, maybe one is a subterm of the other? */
|
|
if (t1s > t2s && termOccurs(t1,t2))
|
|
{
|
|
return (float) t2s / t1s;
|
|
}
|
|
if (t2s > t1s && termOccurs(t2,t1))
|
|
{
|
|
return (float) t1s / t2s;
|
|
}
|
|
return 0;
|
|
}
|
|
else
|
|
{
|
|
/* equal types */
|
|
if (isTermLeaf(t1))
|
|
{
|
|
/* we had established before that they are not equal */
|
|
return 0;
|
|
}
|
|
else
|
|
{
|
|
/* non-leaf recurse */
|
|
if (isTermEncrypt(t1))
|
|
{
|
|
/* encryption */
|
|
return (termDistance(t1->op, t2->op) + termDistance(t1->key, t2->key)) / 2;
|
|
}
|
|
else
|
|
{
|
|
return (termDistance(t1->op1, t2->op1) + termDistance(t1->op2, t2->op2)) / 2;
|
|
}
|
|
}
|
|
}
|
|
}
|