blob: a71a18f8959b1183642841050a853eb7796c0235 [file] [log] [blame]
package com.googlecode.prolog_cafe.lang;
import java.util.ArrayList;
import java.util.List;
/**
* Executes Prolog on the current thread, buffering all solutions.
* <p>
* Whenever a solution is found for the predicate the arguments are deep-copied
* and buffered in a result collection.
*/
public class BufferingPrologControl extends PrologControl {
private int resLimit;
private List resBuffer;
private boolean resSingle;
private Term[] resTemplate;
public BufferingPrologControl() {
}
public BufferingPrologControl(PrologMachineCopy pmc) {
super(pmc);
}
/**
* Initialize one or more packages in the interpreter.
*
* @param pkgs list of package names to initialize.
* @return true if initialization was successful.
*/
public boolean initialize(String... pkgs) {
Term goal = SymbolTerm.intern("true");
Term head = Prolog.Nil;
for (int i = pkgs.length - 1; 0 <= i; i--)
head = new ListTerm(SymbolTerm.intern(pkgs[i]), head);
return execute(Prolog.BUILTIN, "initialization", head, goal);
}
/**
* Determine if the predicate completes successfully.
*
* @param pkg package the functor is declared in. Typically "user".
* @param functor a prolog predicate to execute.
* @param args arguments to pass.
* @return true if the function has at least one solution; false otherwise.
*/
public boolean execute(String pkg, String functor, Term... args) {
return once(pkg, functor, args) != null;
}
/**
* Execute a function and return one solution.
*
* @param pkg package the functor is declared in. Typically "user".
* @param functor a prolog predicate to execute.
* @param arg argument to pass in, and template to return the result with. If
* this is an {@link VariableTerm} the value will be saved and returned
* on success. If this is a structure or list containing variables, the
* variables will be materialized in the result.
* @return a deep copy of {@code arg} for the first solution; null on failure.
*/
public Term once(String pkg, String functor, Term arg) {
setPredicate(pkg, functor, arg);
setResultTemplate(arg);
return (Term) (run(1) ? resBuffer.get(0) : null);
}
/**
* Execute a function and return one solution.
*
* @param pkg package the functor is declared in. Typically "user".
* @param functor a prolog predicate to execute.
* @param args argument to pass in, and template to return the result with. If
* this is an {@link VariableTerm} the value will be saved and returned
* on success. If this is a structure or list containing variables, the
* variables will be materialized in the result.
* @return a deep copy of {@code args} for the first solution; null on
* failure.
*/
public Term[] once(String pkg, String functor, Term... args) {
setPredicate(pkg, functor, args);
setResultTemplate(args);
return (Term[]) (run(1) ? resBuffer.get(0) : null);
}
/**
* Execute a function and return all solutions.
*
* @param pkg package the functor is declared in. Typically "user".
* @param functor a prolog predicate to execute.
* @param arg argument to pass in, and template to return the result with. If
* this is an {@link VariableTerm} the value will be saved and returned
* on success. If this is a structure or list containing variables, the
* variables will be materialized in the result.
* @return a deep copy of {@code arg} for each solution found. Empty list if
* there are no solutions.
*/
public List<Term> all(String pkg, String functor, Term arg) {
setPredicate(pkg, functor, arg);
setResultTemplate(arg);
run(Integer.MAX_VALUE);
return resBuffer;
}
/**
* Execute a function and return all solutions.
*
* @param pkg package the functor is declared in. Typically "user".
* @param functor a prolog predicate to execute.
* @param args argument to pass in, and template to return the result with. If
* this is an {@link VariableTerm} the value will be saved and returned
* on success. If this is a structure or list containing variables, the
* variables will be materialized in the result.
* @return a deep copy of {@code args} for each solution found. Empty list if
* there are no solutions.
*/
public List<Term[]> all(String pkg, String functor, Term... args) {
setPredicate(pkg, functor, args);
setResultTemplate(args);
run(Integer.MAX_VALUE);
return resBuffer;
}
private void setResultTemplate(Term t) {
resTemplate = new Term[] {t};
resSingle = true;
}
private void setResultTemplate(Term[] t) {
resTemplate = t;
resSingle = false;
}
/**
* Execute until the limit is reached.
*
* @param newLimit maximum number of results. Set to 1 if only a single
* attempt is required.
* @return true if at least one result was discovered; false if there are no
* solutions to the predicate.
*/
private boolean run(int newLimit) {
resLimit = newLimit;
resBuffer = new ArrayList(Math.min(newLimit, 16));
executePredicate();
return 0 < resBuffer.size();
}
@Override
public boolean isEngineStopped() {
return resLimit <= resBuffer.size();
}
@Override
protected void success() {
Term[] r = new Term[resTemplate.length];
for (int i = 0; i < resTemplate.length; i++) {
r[i] = engine.copy(resTemplate[i]);
}
resBuffer.add(resSingle ? r[0] : r);
}
@Override
protected void fail() {
resLimit = 0;
}
}