JavaRes/src/atp/Clause.java at master · eprover/JavaRes · GitHub

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A simple implementation of first-order clauses.

See Literal.java for the definition of atoms and literals.

A logical clause in our sense is a multi-set of literals, implicitly

representing the universally quantified disjunction of these literals.

The set of all clauses for a given signature is denoted as

Clauses(P,F,V).

We represent a clause as a list of literals. The actual clause data

structure contains additional information that is useful, but not

strictly necessary from a logic/calculus point of view.

This program is free software; you can redistribute it and/or modify

it under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2 of the License, or

(at your option) any later version.

This program is distributed in the hope that it will be useful,

but WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the

GNU General Public License for more details.

You should have received a copy of the GNU General Public License

along with this program ; if not, write to the Free Software

Foundation, Inc., 59 Temple Place, Suite 330, Boston,

MA 02111-1307 USA

package atp;

import java.io.*;

import java.util.*;

import java.text.*;

/** ***************************************************************

public class Clause {

public static int clauseIDcounter = 0;

public ArrayList<Literal> literals = new ArrayList<Literal>();

public String type = "plain";

public String name = "";

public ArrayList<String> support = new ArrayList<String>(); // Clauses or Formulas from which this clause is derived.

public ArrayList<String> supportsClauses = new ArrayList<String>(); // Clauses this clause supports.

public int depth = 0; // Depth from input

public String rationale = "input"; // If not input, reason for derivation.

public ArrayList<Integer> evaluation = null; // Must be the same order as clause evaluation

// function list in EvalStructure.

public Substitutions subst = new Substitutions(); // The substitutions that support any derived clause.

/** ***************************************************************

public Clause() {

}

/** ***************************************************************

* Print for use by GraphViz. Convert vertical bar to HTML code and

* just print the formula with no informational wrapper.

public Clause(ArrayList<Literal> litlist) {

literals = litlist;

}

/** ***************************************************************

* Print for use by GraphViz. Convert vertical bar to HTML code and

* just print the formula with no informational wrapper.

public String toString(boolean forDot) {

if (!forDot)

return toString();

else {

String temp = Literal.literalList2String(literals);

return temp.replaceAll("\\|", "|");

}

/** ***************************************************************

public ArrayList<String> getConstantStrings() {

ArrayList<String> result = new ArrayList<String>();

for (int i = 0; i < literals.size(); i++)

result.addAll(literals.get(i).getConstantStrings());

return result;

}

/** ***************************************************************

public String toString() {

StringBuffer result = new StringBuffer();

result.append("cnf(" + name + "," + type + "," +

Literal.literalList2String(literals) + ").");

return result.toString();

}

/** ***************************************************************

* Create a string representation of the Clause with reference to

* an inference rule and its supporting axioms if it was generated

* in inference.

public String toStringJustify() {

StringBuffer result = new StringBuffer();

result.append("cnf(" + name + "," + type + "," +

Literal.literalList2String(literals) + ").");

if (support.size() > 0) {

result.append(" : " + rationale + "[");

result.append(support.get(0));

for (int i = 1; i < support.size(); i++) {

result.append(",");

result.append(support.get(i));

}

result.append("]");

}

if (subst != null && subst.subst.keySet().size() > 0) {

result.append(";");

result.append(subst.toString());

}

return result.toString();

}

/** ***************************************************************

* Create a string representation of the Clause's

* inference rule and its supporting axioms if it was generated

* in inference, in TSTP format.

public String toStringTSTPJustify() {

StringBuffer result = new StringBuffer();

if (support.size() > 0) {

result.append("inference(" + rationale + ",[");

result.append(support.get(0));

for (int i = 1; i < support.size(); i++) {

result.append(",");

result.append(support.get(i));

}

result.append("])");

}

return result.toString();

}

/** ***************************************************************

* Print all info about a clause

public String toStringDiag() {

StringBuffer result = new StringBuffer();

result.append(toStringJustify());

result.append(":" + Integer.toString(depth));

return result.toString();

}

/** ***************************************************************

public void createName() {

name = "c" + Integer.toString(clauseIDcounter);

clauseIDcounter++;

}

/** ***************************************************************

public void addEval(ArrayList<Integer> e) {

evaluation = e;

}

/** ***************************************************************

public Clause deepCopy() {

return deepCopy(0);

}

/** ***************************************************************

* @param start is the starting index of the literal list to copy

public Clause deepCopy(int start) {

Clause result = new Clause();

result.name = name;

result.type = type;

result.rationale = rationale;

for (int i = 0; i < support.size(); i++)

result.support.add(support.get(i));

for (int i = start; i < literals.size(); i++)

result.literals.add(literals.get(i).deepCopy());

if (subst != null)

result.subst = subst.deepCopy();

return result;

}

/** ***************************************************************

* Check to see if the contents of two clauses are equal. Ignore

* all meta-information such as clause name, type and information

* that tracks how it was created. Note that normalizeVariables()

* should first be called so that identical clauses will have

* syntactically equal variable names.

public boolean equals(Object c_obj) {

assert !c_obj.getClass().getName().equals("Clause") : "Clause() passed object not of type Clause";

Clause c = (Clause) c_obj;

if (literals.size() != c.literals.size())

return false;

for (int i = 0; i < literals.size(); i++)

if (!literals.get(i).equals(c.literals.get(i)))

return false;

return true;

}

/** ***************************************************************

* should never be called so throw an error.

public int hashCode() {

assert false : "Clause not designed";

return 0;

}

/** ***************************************************************

public int length() {

return literals.size();

}

/** ***************************************************************

public void add(Literal l) {

literals.add(l);

}

/** ***************************************************************

public void addAll(ArrayList<Literal> l) {

literals.addAll(l);

}

/** ***************************************************************

* Parse a clause. A clause in (slightly simplified) TPTP-3 syntax

* is written as

* cnf(<name>, <type>, <literal list>).

* where <name> is a lower-case ident, type is a lower-case ident

* from a specific list, and <literal list> is a "|" separated list

* of literals, optionally enclosed in parenthesis.

* For us, all clause types are essentially the same, so we only

* distinguish "axiom", "negated_conjecture", and map everything else

* to "plain".

* @return the parsed clause. Note also that this is the side effect

* on the clause instance

public static Clause parse(Lexer lex) {

Clause result = new Clause();

try {

//System.out.println("INFO in Clause.parse(): " + lex.literal);

lex.next();

//if (st.ttype == '%')

// return this;

if (!lex.literal.equals("cnf"))

throw new Exception("\"cnf\" expected. Instead found '" + lex.literal + "' with clause so far " + result);

lex.next();

if (!lex.type.equals(Lexer.OpenPar))

throw new Exception("Open paren expected. Instead found '" + lex.literal + "' with clause so far " + result);

lex.next();

if (lex.type == Lexer.IdentLower)

result.name = lex.literal;

else {

System.out.println("Warning in Clause.parse(): Identifier expected. Instead found '" + lex.literal + "' with clause so far " + result);

System.out.println("Accepting non-identifier anyway.");

result.name = lex.literal;

}

lex.next();

if (!lex.type.equals(Lexer.Comma))

throw new Exception("Comma expected. Instead found '" + lex.literal + "' with clause so far " + result);

lex.next();

if (lex.type == Lexer.IdentLower) {

result.type = lex.literal;

//if (!type.equals("axiom") && !type.equals("negated_conjecture"))

// type = "plain";

}

else

throw new Exception("Clause type enumeration expected. Instead found '" + lex.literal + "' with clause so far " + result);

lex.next();

if (!lex.type.equals(Lexer.Comma))

throw new Exception("Comma expected. Instead found '" + lex.literal + "' with clause so far " + result);

String s = lex.look();

//System.out.println("INFO in Clause.parse() (2): found token: " + s);

if (s.equals(Lexer.OpenPar)) {

//System.out.println("INFO in Clause.parse(): found open paren at start of bare clause");

lex.next();

result.literals = Literal.parseLiteralList(lex);

lex.next();

if (!lex.type.equals(Lexer.ClosePar))

throw new Exception("Literal list close paren expected. Instead found '" + lex.literal + "' with clause so far " + result);

}

else {

result.literals = Literal.parseLiteralList(lex);

}

lex.next();

if (!lex.type.equals(Lexer.ClosePar)) {

//System.out.println("Warning in Clause.parse(): Clause close paren expected. Instead found '" + lex.literal + "' with clause so far " + this);

//System.out.println("Discarding remainder of line.");

while (lex.type != Lexer.FullStop && lex.type != Lexer.EOFToken)

lex.next();

return result;

}

lex.next();

if (!lex.type.equals(Lexer.FullStop))

throw new Exception("Period expected. Instead found '" + lex.literal + "' with clause so far " + result);

//System.out.println("INFO in Clause.parse(): completed parsing: " + this);

return result;

}

catch (Exception ex) {

Prover2.errors = "input error";

if (lex.type == Lexer.EOFToken)

return result;

System.out.println("Error in Clause.parse(): " + ex.getMessage());

System.out.println("Error in Term.parseTermList(): token:" + lex.literal);

ex.printStackTrace();

}

return null;

}

/** ***************************************************************

public static Clause string2Clause(String s) {

Lexer lex = new Lexer(s);

return Clause.parse(lex);

}

/** ***************************************************************

* Return true if the clause is empty.

public boolean isEmpty() {

return literals.size() == 0;

}

/** ***************************************************************

* Return true if the clause is a unit clause.

public boolean isUnit() {

return literals.size() == 1;

}

/** ***************************************************************

* Return true if the clause is a Horn clause.

public boolean isHorn() {

ArrayList<Literal> tmp = new ArrayList<Literal>();

for (int i = 0; i < literals.size(); i++)

if (literals.get(i).isPositive())

tmp.add(literals.get(i));

return tmp.size() <= 1;

}

/** ***************************************************************

* Return the indicated literal of the clause. Position is an

* integer from 0 to litNumber (exclusive).

public Literal getLiteral(int position) {

if (position >= 0 && position < literals.size())

return literals.get(position);

else

return null;

}

/** ***************************************************************

* Insert all variables in self into the set res and return it.

public ArrayList<Term> collectVars() {

ArrayList<Term> res = new ArrayList<Term>();

for (int i = 0; i < literals.size(); i++)

res.addAll(literals.get(i).collectVars());

return res;

}

/** ***************************************************************

* Collect function- and predicate symbols into the signature.

public Signature collectSig(Signature sig) {

for (Literal l : literals)

sig = l.collectSig(sig);

return sig;

}

/** ***************************************************************

* Return the symbol-count weight of the clause.

public int weight(int fweight, int vweight) {

int res = 0;

for (int i = 0; i < literals.size(); i++)

res = res + literals.get(i).weight(fweight, vweight);

return res;

}

/** ***************************************************************

* Return an instantiated copy of self. Name and type are copied

* and need to be overwritten if that is not desired.

public Clause substitute(Substitutions subst) {

//System.out.println("INFO in Clause.instantiate(): " + subst);

//System.out.println("INFO in Clause.instantiate(): " + this);

Clause newC = deepCopy();

newC.literals = new ArrayList<Literal>();

for (int i = 0; i < literals.size(); i++)

newC.literals.add(literals.get(i).substitute(subst));

//System.out.println("INFO in Clause.instantiate(): " + newC);

return newC;

}

/** ***************************************************************

* Return a copy of self with fresh variables.

public Clause freshVarCopy() {

ArrayList<Term> vars = collectVars();

Substitutions s = Substitutions.freshVarSubst(vars);

subst.addAll(s);

return substitute(s);

}

/** ***************************************************************

* Return a copy of self with variables that are renumbered from 0,

* which will make clauses that are equal except for their variable

* names, syntactically equal.

public Clause normalizeVarCopy() {

ArrayList<Term> vars = collectVars();

int varCounter = 0;

Substitutions s = new Substitutions();

for (int i = 0; i < vars.size(); i++) {

Term newTerm = new Term();

newTerm.t = "VAR" + Integer.toString(varCounter++);

s.addSubst(vars.get(i), newTerm);

}

//System.out.println("INFO in Clause.normalizeVarCopy(): subst: " + s);

Clause c = deepCopy();

subst.addAll(s);

return c.substitute(s);

}

/** ***************************************************************

* Remove duplicated literals from clause.

public void removeDupLits() {

ArrayList<Literal> res = new ArrayList<Literal>();

for (int i = 0; i < literals.size(); i++) {

if (!Literal.litInLitList(literals.get(i),res))

res.add(literals.get(i));

}

literals = res;

}

/** ***************************************************************

* Check if a clause is a simple tautology, i.e. if it contains

* two literals with the same atom, but different signs.

public boolean isTautology() {

if (literals.size() < 2)

return false;

for (int i = 0; i < literals.size(); i++) {

for (int j = 1; j < literals.size(); j++) {

if (literals.get(i).isOpposite(literals.get(j)))

return true;

}

return false;

}

/** ***************************************************************

* ************ UNIT TESTS *****************

public static String str1 = "";

/** ***************************************************************

* Setup function for clause/literal unit tests. Initialize

* variables needed throughout the tests.

public static void setup() {

str1 = "cnf(test1,axiom,p(a)|p(f(X))).\n" +

"cnf(test2,axiom,(p(a)|p(f(X)))).\n" +

"cnf(test3,lemma,(p(a)|~p(f(X)))).\n" +

"cnf(taut,axiom,p(a)|q(a)|~p(a)).\n" +

"cnf(dup,axiom,p(a)|q(a)|p(a)).\n" +

"cnf(c6,axiom,f(f(X1,X2),f(X3,g(X4,X5)))!=f(f(g(X4,X5),X3),f(X2,X1))|k(X1,X1)!=k(a,b)).\n" +

"cnf(c7,axiom,f(f(X10,X2),f(X30,g(X4,X5)))!=f(f(g(X4,X5),X30),f(X2,X10))|k(X10,X10)!=k(a,b)).\n";

}

/** ***************************************************************

* Test that basic literal parsing works correctly.

public static void testClauses() {

System.out.println("INFO in Clause.testClauses(): expected results: \n" + str1);

System.out.println("results:");

Lexer lex = new Lexer(str1);

Clause c1 = Clause.parse(lex);

assert c1.toString().equals("cnf(test1,axiom,p(a)|p(f(X))).") :

"Failure. " + c1.toString() + " not equal to cnf(test1,axiom,p(a)|p(f(X))).";

System.out.println("c1: " + c1);

Clause c2 = Clause.parse(lex);

assert c2.toString().equals("cnf(test2,axiom,(p(a)|p(f(X)))).") :

"Failure. " + c2.toString() + " not equal to cnf(test2,axiom,(p(a)|p(f(X)))).";

System.out.println("c2: " + c2);

Clause c3 = Clause.parse(lex);

assert c3.toString().equals("cnf(test3,lemma,(p(a)|~p(f(X)))).") :

"Failure. " + c3.toString() + " not equal to cnf(test3,lemma,(p(a)|~p(f(X)))).";

System.out.println("c3: " + c3);

Clause c4 = Clause.parse(lex);

assert c4.toString().equals("cnf(taut,axiom,p(a)|q(a)|~p(a)).") :

"Failure. " + c4.toString() + " not equal to cnf(taut,axiom,p(a)|q(a)|~p(a)).";

System.out.println("c4: " + c4);

Clause c5 = Clause.parse(lex);

assert c5.toString().equals("cnf(dup,axiom,p(a)|q(a)|p(a)).") :

"Failure. " + c5.toString() + " not equal to cnf(dup,axiom,p(a)|q(a)|p(a)).";

System.out.println("c5: " + c5);

Clause c6 = Clause.parse(lex);

assert c6.toString().equals("cnf(c6,axiom,(f(f(X1,X2),f(X3,g(X4,X5)))!=f(f(g(X4,X5),X3),f(X2,X1))|k(X1,X1)!=k(a,b))).") :

"Failure. " + c6.toString() + " not equal to cnf(c6,axiom,(f(f(X1,X2),f(X3,g(X4,X5)))!=f(f(g(X4,X5),X3),f(X2,X1))|k(X1,X1)!=k(a,b))).";

System.out.println("c6: " + c6);

Clause c7 = Clause.parse(lex);

assert c7.normalizeVarCopy().equals(c6.normalizeVarCopy());

System.out.println("c6: " + c6);

System.out.println("c6 normalized: " + c6.normalizeVarCopy());

System.out.println("c7: " + c7);

System.out.println("c7 normalized: " + c7.normalizeVarCopy());

}

/** ***************************************************************

* Test method for this class.

public static void main(String[] args) {

setup();

testClauses();

}

JavaRes/src/atp/Clause.java at master · eprover/JavaRes · GitHub

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