ListTerm deleteFromList(Term element, ListTerm l, Unifier un) {
Unifier bak = un;
ListTerm r = new ListTermImpl();
ListTerm last = r;
for (Term t : l) {
boolean u = un.unifies(element, t);
if (u) un = bak.clone();
else last = last.append(t.clone());
}
return r;
}
@Override
public Object execute(TransitionSystem ts, Unifier un, Term[] args) throws Exception {
checkArguments(args);
if (args[0].isNumeric() && args[1].isString()) {
return un.unifies(
args[2], deleteFromString((int) ((NumberTerm) args[0]).solve(), (StringTerm) args[1]));
}
if (args[0].isNumeric() && args[1].isList()) {
return un.unifies(
args[2], deleteFromList((int) ((NumberTerm) args[0]).solve(), (ListTerm) args[1]));
}
if (args[0].isString() && args[1].isString()) {
return un.unifies(args[2], deleteFromString((StringTerm) args[0], (StringTerm) args[1]));
}
// first element as term
if (args[1].isList()) {
return un.unifies(args[2], deleteFromList(args[0], (ListTerm) args[1], un.clone()));
}
throw new JasonException("Incorrect use of the internal action '.delete' (see documentation).");
}