public override bool Evaluate(Resource[] args, ref Resource @object) {
if (args.Length != 2) return false;
if (args[0] == null || !(args[0] is Literal)) return false;
if (args[1] == null || !(args[1] is Literal)) return false;
try {
Decimal left = (Decimal)Convert.ChangeType( ((Literal)args[0]).ParseValue() , typeof(Decimal) );
Decimal right = (Decimal)Convert.ChangeType( ((Literal)args[1]).ParseValue() , typeof(Decimal) );
Resource newvalue = Literal.FromValue(Evaluate(left, right));
if (@object == null) {
@object = newvalue;
return true;
} else {
return @object.Equals(newvalue);
}
} catch (FormatException) {
return false;
}
}
public override bool Evaluate(Resource[] args, ref Resource @object) {
Decimal sum = InitialValue;
foreach (Resource r in args) {
if (r == null) return false;
if (!(r is Literal)) return false;
try {
Decimal v = (Decimal)Convert.ChangeType( ((Literal)r).ParseValue() , typeof(Decimal) );
sum = Combine(sum, v);
} catch (FormatException) {
return false;
}
}
Resource newvalue = Literal.FromValue(sum);
if (@object == null) {
@object = newvalue;
return true;
} else {
return @object.Equals(newvalue);
}
}
private static bool unify(Resource s, Hashtable senv, Resource d, Hashtable denv, bool f)
{
if (s is Variable) {
Resource sval = evaluate(s, senv);
if (sval != null) return unify(sval, senv, d, denv, f);
else return true;
} else if (d is Variable) {
Resource dval = evaluate(d, denv);
if (dval != null) {
return unify(s, senv, dval, denv, f);
} else {
if (f) denv[d] = evaluate(s, senv);
return true;
}
} else if (s.Equals(d)) {
return true;
} else {
return false;
}
}