blob: 3c11e854b2563a4064bdec789302afbfba05148a [file] [log] [blame]
package com.googlecode.prolog_cafe.lang;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.LinkedList;
/**
* Superclass of any predicate's implementation class.
* <p>
* Concrete implementations must provide a definition of the Operation's
* {@link Operation#exec(Prolog)} method. On a successful execution the
* method must return {@link #cont}.
* <p>
* To be compatible with the {@code am2j} compiler implementations must
* define a constructor matching the signature:
* <pre>
* public ClassName(Term arg1, Term arg2, ..., Operation cont) {
* // save arg1, arg2
* this.cont = cont;
* }
* </pre>
*/
public abstract class Predicate extends Operation {
/**
* Holds the continuation goal of this predicate.
* <p>
* In a Prolog program this is the next operation to perform if this operation
* was executed successfully.
*/
public Operation cont;
@Override
public String toString() {
LinkedList<Class> toScan = new LinkedList<Class>();
Class clazz = getClass();
while (clazz != Predicate.class) {
toScan.addFirst(clazz);
clazz = clazz.getSuperclass();
}
StringBuffer sb = new StringBuffer();
sb.append(PredicateEncoder.decodeFunctor(getClass().getName()));
boolean first = true;
for (Class c : toScan) {
for (Field f : c.getDeclaredFields()) {
if ((f.getModifiers() & Modifier.STATIC) == 0
&& f.getType() == Term.class
&& f.getName().startsWith("arg")) {
Term val;
try {
f.setAccessible(true);
val = (Term) f.get(this);
} catch (IllegalArgumentException e) {
continue;
} catch (IllegalAccessException e) {
continue;
}
if (first) {
sb.append('(');
first = false;
} else
sb.append(", ");
sb.append(val);
}
}
}
if (!first)
sb.append(')');
return sb.toString();
}
public static abstract class P1 extends Predicate {
protected Term arg1;
}
public static abstract class P2 extends Predicate {
protected Term arg1;
protected Term arg2;
}
public static abstract class P3 extends Predicate {
protected Term arg1;
protected Term arg2;
protected Term arg3;
}
public static abstract class P4 extends Predicate {
protected Term arg1;
protected Term arg2;
protected Term arg3;
protected Term arg4;
}
}