public object Evaluate(Frame environment, Expression expression)
{
List<Expression> operands = expression.GetRest();
if (operands.Count < 2)
{
throw new Exception("Invalid define arguments");
}
bool isFunctionDeclaration = false;
if (operands[0] is Combination)
{
isFunctionDeclaration = true;
}
String name = operands[0].GetFirst().ToString();
List<string> parameters = new List<string>();
foreach (Expression expr in operands[0].GetRest())
{
parameters.Add(expr.ToString());
}
List<Expression> body = new List<Expression>(operands.Count - 1);
if (!isFunctionDeclaration)
{
var definitionValue = environment.Evaluate(operands[1]);
if (definitionValue is Lambda)
{
environment.AddBinding(name, (Lambda)definitionValue);
}
else
{
environment.AddBinding(name, new Identity(environment,definitionValue));
}
return name;
}
for (int i = 1; i < operands.Count; i++)
{
body.Add(operands[i]);
}
environment.AddBinding(name, new Lambda(environment,parameters, body));
return name;
}