private static Expr Map(List <Expr> args, Dictionary <string, Expr> env)
{
// first thing in args should be a procedure
if (args.Count < 2)
{
throw new EvaluatorException("the expected number of arguments does not match the given number");
}
Expr proc = args[0];//.eval(env);
List <Expr> evaled_lists = new List <Expr>();
List <Expr> proc_calls = new List <Expr>();
Expr arg;
for (int i = 1; i < args.Count; i++)
{
arg = args[i].eval(env);
if (arg.GetType() != typeof(ConsExpr))
{
throw new EvaluatorException("map: contract violation\n expected: list?");
}
evaled_lists.Add((ConsExpr)arg);
}
while (evaled_lists[0].GetType() != typeof(EmptyExpr))
{
List <Expr> proc_args = new List <Expr>();
for (int j = 0; j < evaled_lists.Count; j++)
{
if (evaled_lists[j].GetType() == typeof(EmptyExpr))
{
throw new EvaluatorException("map: lists must be of same length");
}
ConsExpr arg_ = (ConsExpr)evaled_lists[j];
// check that all lists are proper lists
if (arg_.getRest().GetType() != typeof(ConsExpr) &&
arg_.getRest().GetType() != typeof(EmptyExpr))
{
throw new EvaluatorException("map: contract violation\n expected: list?");
}
proc_args.Add(arg_.getFirst());
evaled_lists[j] = arg_.getRest();
}
proc_calls.Add(new AppExpr(proc, proc_args, env));
}
// check that all lists end
for (int j = 1; j < evaled_lists.Count; j++)
{
if (evaled_lists[j].GetType() != typeof(EmptyExpr))
{
throw new EvaluatorException("map: all lists must have same size");
}
}
return(List(proc_calls, env));
}
private static Expr Car(List <Expr> arg, Dictionary <string, Expr> env)
{
if (arg.Count != 1)
{
throw new EvaluatorException("expected cons");
}
Expr cons = arg[0].eval(env);
if (cons.GetType() != typeof(ConsExpr))
{
throw new EvaluatorException("car: contract violation\n expected: pair?");
}
ConsExpr cons_ = (ConsExpr)cons;
return(cons_.getFirst());
}