551 lines
12 KiB
C
551 lines
12 KiB
C
/**
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*@file knowledge.c
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*\brief Procedures concerning knowledge structures.
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*
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* The main issue of this code is to maintain the minimal property of the knowledge set.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include "termlist.h"
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#include "knowledge.h"
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#include "system.h"
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#include "debug.h"
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#include "error.h"
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/*
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* Knowledge stuff
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*
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* Note that a really weird thing is going on involving unpropagated substitutions.
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* Idea:
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*
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* 1. Substitute terms by filling in ->subst.
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* Now, either:
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* 2a. Undo this by knowledgeUndo.
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* 2b. Propagate it, modifying the knowledge beyond repair by knowledgeSubstDo. Now inKnowledge works again.
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* 2c. inKnowledge/knowledgeSet if something is in the knowledge: this does not consider the substitutions!, and
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* they now have some overhead.
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*/
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//! Open knowledge code.
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void
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knowledgeInit (void)
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{
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return;
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}
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//! Close knowledge code.
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void
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knowledgeDone (void)
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{
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}
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//! Allocate a fresh memory block the size of a knowledge struct.
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/**
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* Memory will not be initialized.
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*@return Pointer to a fresh memory block.
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*/
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Knowledge
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makeKnowledge ()
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{
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return (Knowledge) malloc (sizeof (struct knowledge));
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}
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//! Create a new empty knowledge structure.
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/**
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*@return Pointer to an empty knowledge structure.
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*/
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Knowledge
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emptyKnowledge ()
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{
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Knowledge know;
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know = makeKnowledge ();
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know->basic = NULL;
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know->encrypt = NULL;
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know->inverses = NULL;
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know->vars = NULL;
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return know;
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}
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//! Duplicate a knowledge structure.
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/**
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* Makes copies using termlistShallow() of knowledge::basic, knowledge::encrypt and
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* knowledge::vars.
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* For the inverses, only the pointer is copied.
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*@param know The knowledge structure to be copied.
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*@return A pointer to a new memory struct.
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*\sa termlistShallow(), knowledgeDelete()
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*/
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Knowledge
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knowledgeDuplicate (Knowledge know)
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{
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Knowledge newknow;
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if (know == NULL)
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{
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warning ("Trying to copy empty knowledge.");
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return NULL;
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}
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newknow = makeKnowledge ();
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newknow->basic = termlistShallow (know->basic);
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newknow->encrypt = termlistShallow (know->encrypt);
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newknow->vars = termlistShallow (know->vars);
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newknow->inverses = know->inverses;
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return newknow;
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}
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//! Delete a knowledge set.
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/**
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* Typically used to destroy something made with knowledgeDuplicate().
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*\sa knowledgeDuplicate()
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*/
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void
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knowledgeDelete (Knowledge know)
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{
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if (know != NULL)
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{
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termlistDelete (know->basic);
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termlistDelete (know->encrypt);
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termlistDelete (know->vars);
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free (know);
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}
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}
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//! Destroy a knowledge set.
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/**
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* Unlike knowledgeDelete(), uses termlistDestroy() to remove knowledge::basic,
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* knowledge::encrypt and knowledge::vars substructures.
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*\sa knowledgeDelete()
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*/
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void
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knowledgeDestroy (Knowledge know)
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{
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if (know != NULL)
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{
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termlistDestroy (know->basic);
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termlistDestroy (know->encrypt);
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termlistDestroy (know->vars);
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// termlistDestroy(know->inverses);
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free (know);
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}
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}
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//! Add a term to a knowledge set.
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/**
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*@param know The knowledge set.
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*@param term The term to be added.
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*@return True iff the term was actually new, and added.
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*/
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int
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knowledgeAddTerm (Knowledge know, Term term)
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{
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if (know == NULL)
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{
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warning ("Trying to add term to uninitialised (NULL) Know pointer.");
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return 1;
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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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/* for tuples, simply recurse for components */
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if (isTermTuple (term))
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{
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int status;
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status = knowledgeAddTerm (know, TermOp1 (term));
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return knowledgeAddTerm (know, TermOp2 (term)) || status;
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}
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/* test whether we knew it before */
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if (inKnowledge (know, term))
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return 0;
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/* adding variables? */
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know->vars = termlistAddVariables (know->vars, term);
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knowledgeSimplify (know, term);
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if (isTermLeaf (term))
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{
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know->basic = termlistAdd (know->basic, term);
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}
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if (term->type == ENCRYPT)
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{
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Term invkey = inverseKey (know->inverses, TermKey (term));
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if (inKnowledge (know, invkey))
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{
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/* we can decrypt it */
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knowledgeAddTerm (know, TermOp (term));
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if (!inKnowledge (know, TermKey (term)))
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{
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/* we know the op now, but not the key, so add it anyway */
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know->encrypt = termlistAdd (know->encrypt, term);
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}
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}
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else
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{
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/* we cannot decrypt it, and from the initial test we know we could not construct it */
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know->encrypt = termlistAdd (know->encrypt, term);
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}
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termDelete (invkey);
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}
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return 1;
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}
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//! Try to simplify knowledge based on a term.
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/**
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*@param know A knowledge set.
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*@param key A key, i.e. it can decrypt anything that was encrypted with term^{-1}.
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*/
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void
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knowledgeSimplify (Knowledge know, Term key)
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{
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Termlist tldecrypts = NULL;
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Termlist scan = know->encrypt;
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Term invkey = inverseKey (know->inverses, key);
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while (scan != NULL)
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{
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if (isTermEqual (TermKey (scan->term), invkey))
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{
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tldecrypts = termlistAdd (tldecrypts, TermOp (scan->term));
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know->encrypt = termlistDelTerm (scan);
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scan = know->encrypt;
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}
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else
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scan = scan->next;
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}
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termDelete (invkey);
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knowledgeAddTermlist (know, tldecrypts);
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termlistDelete (tldecrypts);
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}
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//! Add a termlist to the knowledge.
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/*
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*@return True iff there was at least one new item.
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*\sa knowledgeAddTerm()
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*/
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int
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knowledgeAddTermlist (Knowledge know, Termlist tl)
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{
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int flag = 0;
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while (tl != NULL)
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{
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flag = knowledgeAddTerm (know, tl->term) || flag;
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tl = tl->next;
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}
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return flag;
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}
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//! Add an inverse pair to the knowledge
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void
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knowledgeAddInverse (Knowledge know, Term t1, Term t2)
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{
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know->inverses = termlistAdd (know->inverses, t1);
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know->inverses = termlistAdd (know->inverses, t2);
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return;
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}
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//! Set an inverse pair list for the knowledge.
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/**
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* List pointer is simply copied, so don't delete it later!
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*/
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void
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knowledgeSetInverses (Knowledge know, Termlist tl)
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{
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know->inverses = tl;
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}
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//! Is a term a part of the knowledge?
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/**
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*@param know The knowledge set.
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*@param term The term to be inferred.
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*@return True iff the term can be inferred from the knowledge set.
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*/
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int
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inKnowledge (const Knowledge know, Term term)
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{
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mindwipe (know, inKnowledge (know, term));
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/* if there is no term, then it's okay 'fur sure' */
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if (term == NULL)
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return 1;
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/* if there is a term, but no knowledge, we're in trouble */
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if (know == NULL)
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return 0;
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term = deVar (term);
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if (isTermLeaf (term))
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{
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return inTermlist (know->basic, term);
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}
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if (term->type == ENCRYPT)
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{
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return inTermlist (know->encrypt, term) ||
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(inKnowledge (know, TermKey (term))
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&& inKnowledge (know, TermOp (term)));
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}
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if (term->type == TUPLE)
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{
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return (inTermlist (know->encrypt, term) ||
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(inKnowledge (know, TermOp1 (term)) &&
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inKnowledge (know, TermOp2 (term))));
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}
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return 0; /* unrecognized term type, weird */
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}
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//! Compare two knowledge sets.
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/**
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* This does not check currently for equivalence of inverse sets, which it should.
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*@return True iff both knowledge sets are equal.
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*/
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int
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isKnowledgeEqual (Knowledge know1, Knowledge know2)
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{
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if (know1 == NULL || know2 == NULL)
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{
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if (know1 == NULL && know2 == NULL)
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return 1;
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else
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return 0;
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}
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if (!isTermlistEqual (know1->encrypt, know2->encrypt))
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return 0;
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return isTermlistEqual (know1->basic, know2->basic);
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}
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//! Print a knowledge set.
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void
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knowledgePrint (Knowledge know)
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{
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indent ();
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if (know == NULL)
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{
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eprintf ("Empty.\n");
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return;
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}
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eprintf (" [Basic]: ");
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termlistPrint (know->basic);
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eprintf ("\n");
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indent ();
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eprintf (" [Encrp]: ");
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termlistPrint (know->encrypt);
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eprintf ("\n");
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indent ();
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eprintf (" [Vars]: ");
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termlistPrint (know->vars);
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eprintf ("\n");
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}
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//! Print a knowledge set, short version (no newline)
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void
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knowledgePrintShort (const Knowledge know)
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{
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indent ();
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if (know == NULL)
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{
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eprintf ("Empty");
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return;
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}
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if (know->basic != NULL)
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{
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termlistPrint (know->basic);
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if (know->encrypt != NULL);
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{
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eprintf (", ");
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}
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}
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if (know->encrypt != NULL)
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{
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termlistPrint (know->encrypt);
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}
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}
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//! Print the inverses list of a knowledge set.
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void
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knowledgeInversesPrint (Knowledge know)
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{
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Termlist tl;
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int after = 0;
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if (know == NULL)
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{
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eprintf ("Empty knowledge.");
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return;
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}
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tl = knowledgeGetInverses (know);
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if (tl == NULL)
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{
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eprintf ("None.");
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}
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else
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{
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while (tl != NULL && tl->next != NULL)
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{
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if (after)
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{
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eprintf (",");
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}
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eprintf ("(");
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termPrint (tl->term);
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eprintf (",");
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termPrint (tl->next->term);
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eprintf (")");
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after = 1;
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tl = tl->next->next;
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}
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}
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}
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//! Yield the set of representatives for the knowledge.
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/**
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* Note: this is a shallow copy, and needs to be termlistDelete'd.
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*\sa termlistDelete()
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*/
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Termlist
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knowledgeSet (const Knowledge know)
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{
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Termlist tl1, tl2;
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tl1 = termlistShallow (know->basic);
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tl2 = termlistShallow (know->encrypt);
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return termlistConcat (tl1, tl2);
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}
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//! Get the inverses pointer of the knowledge.
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/**
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* Essentially the inverse function of knowledgeSetInverses()
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*/
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Termlist
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knowledgeGetInverses (const Knowledge know)
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{
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if (know == NULL)
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return NULL;
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else
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return know->inverses;
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}
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//! Get all basic elements in the knowledge
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/**
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* This function is used by match_basic, to determine all basic elements in the knowledge set.
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* Most of the time this doesn't even change, so it might become a parameter of knowledge.
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* For now, this will have to do.
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*
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*@todo Investigate whether the basics in the knowledge set should be a parameter of knowledge, as it doesn't change very often.
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*/
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__inline__ Termlist
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knowledgeGetBasics (const Knowledge know)
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{
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return termlistAddBasics (termlistAddBasics (NULL, know->basic),
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know->encrypt);
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}
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//! check whether any substitutions where made in a knowledge set.
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/**
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* Typically, when a substitution is made, a knowledge set has to be reconstructed.
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* This procedure detects this by checking knowledge::vars.
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*@return True iff an open variable was later closed by a substitution.
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*\sa knowledgeReconstruction()
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*/
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int
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knowledgeSubstNeeded (const Knowledge know)
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{
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Termlist tl;
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if (know == NULL)
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return 0;
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tl = know->vars;
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while (tl != NULL)
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{
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if (tl->term->subst != NULL)
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return 1;
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tl = tl->next;
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}
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return 0;
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}
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//! Reconstruct a knowledge set.
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/**
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* This is useful after e.g. substitutions.
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* Just rebuilds the knowledge in a new (shallow) copy.
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*@return The pointer to the new knowledge.
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*\sa knowledgeSubstNeeded()
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*/
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Knowledge
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knowledgeReconstruction (const Knowledge know)
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{
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Knowledge newknow = emptyKnowledge ();
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newknow->inverses = know->inverses;
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knowledgeAddTermlist (newknow, know->basic);
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knowledgeAddTermlist (newknow, know->encrypt);
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return newknow;
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}
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//! Propagate any substitutions just made.
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/**
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* This usually involves reconstruction of the complete knowledge, which is
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* 'cheaper' than a thorough analysis, so we always make a copy.
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*\sa knowledgeReconstruction()
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*/
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Knowledge
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knowledgeSubstDo (const Knowledge know)
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{
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/* otherwise a copy (for deletion) is returned. */
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return knowledgeReconstruction (know);
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}
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//! Undo substitutions that were not propagated yet.
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/**
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* Undo the substitutions just made. Note that this does not work anymore after knowledgeSubstDo()
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*/
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void
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knowledgeSubstUndo (const Knowledge know)
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{
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Termlist tl;
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tl = know->vars;
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while (tl != NULL)
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{
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tl->term->subst = NULL;
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tl = tl->next;
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}
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}
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//! Yield the minimal set of terms that are in some knowledge, but not in some other set.
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/**
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* Yield a termlist (or NULL) that represents the reduced items that are
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* in the new set, but not in the old one.
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*@param oldk The old knowledge.
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*@param newk The new knowledge, possibly with new terms.
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*@return A termlist of miminal terms in newk, but not in oldk.
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*/
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Termlist
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knowledgeNew (const Knowledge oldk, const Knowledge newk)
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{
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Termlist newtl;
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void addNewStuff (Termlist tl)
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{
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while (tl != NULL)
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{
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if (!inKnowledge (oldk, tl->term))
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{
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newtl = termlistAdd (newtl, tl->term);
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}
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tl = tl->next;
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}
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}
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newtl = NULL;
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addNewStuff (newk->basic);
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addNewStuff (newk->encrypt);
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return newtl;
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}
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