public override object Evaluate(Water.List expressions)
{
//Push a stack frame
Water.Environment.Push();
// Evaluate local variables.
Water.List expressions_to_eval = expressions.Copy();
Water.List values = new Water.List();
bool hasRest = false;
foreach (Water.Identifier parameter in this.Parameters)
{
if (hasRest)
{
throw new Water.Error("Cannot have parameters after a rest parameter in function " + this._name);
}
if (IsRest(parameter))
{
//Add the rest.
Water.List rest = new Water.List();
foreach (object expression in expressions_to_eval)
{
rest.Add(Water.Evaluator.Evaluate(expression));
}
expressions_to_eval.Clear();
values.Add(rest);
hasRest = true;
}
else if (IsOptional(parameter))
{
//If it doesn't exist add null.
if (expressions_to_eval.Count == 0)
{
values.Add(null);
}
else
{
object value = Water.Evaluator.Evaluate(expressions_to_eval.First());
values.Add(value);
expressions_to_eval = expressions_to_eval.NotFirst();
}
}
else if (IsUnevaluated(parameter))
{
values.Add(expressions_to_eval.First());
expressions_to_eval = expressions_to_eval.NotFirst();
}
else
{
//Throw exception if null.
if (expressions_to_eval.Count == 0)
{
throw new Water.Error("Parameter is required: " + parameter.Value);
}
else
{
object value = Water.Evaluator.Evaluate(expressions_to_eval.First());
if (value == null)
{
throw new Water.Error("Parameter is required: " + parameter.Value);
}
values.Add(value);
expressions_to_eval = expressions_to_eval.NotFirst();
}
}
}
if (expressions_to_eval.Count > 0)
{
throw new Water.Error("Too many expressions passed to function: " + this._name);
}
// Push local variables.
int i = 0;
foreach (Water.Identifier parameter in this.Parameters)
{
if (Water.Environment.IsConstant(parameter.Value))
{
throw new Water.Error("Constant \"" + parameter.Value + "\" is already defined.");
}
if (IsOptional(parameter))
{
string name = GetOptional(parameter);
Water.Environment.DefineVariable(name, values[i]);
}
else if (IsRest(parameter))
{
string name = GetRest(parameter);
Water.Environment.DefineVariable(name, values[i]);
}
else if (IsUnevaluated(parameter))
{
string name = GetUnevaluated(parameter);
Water.Environment.DefineVariable(name, values[i]);
}
else
{
Water.Environment.DefineVariable(parameter.Value, values[i]);
}
i++;
}
//Interpret the function.
Water.Interpreter.Interpret(new StatementIterator(this.Statements, false));
//Pop a stack frame.
Water.Environment.Pop();
object returnValue = Water.Environment.ReturnValue;
Water.Environment.Return = false;
Water.Environment.ReturnValue = null;
return(returnValue);
}