protected static void AssertArgsMinimum(string name, string message, int expected, int given, LinkedList <Value> argv, Syntax expression)
{
if (given < expected)
{
throw SchemeError.ArityError(name, message, expected, given, argv, expression);
}
}
// (cond () ...)
public static AST Expand(Syntax stx, Environment env)
{
var list = stx.AsLinkedList <Value>(); //< list of syntax objects
var argc = GetArgsCount(list);
var keyword = list[0].AsSyntax();
LinkedList <Value> allcases = null;
LinkedList <Value> elsecase = null;
var curent = list.GetNodeAtIndex(1);
while (curent != null)
{
var conditional_stx = curent.Value.AsSyntax();
if (elsecase != null)
{
throw SchemeError.SyntaxError("cond", "unexpected expression after condition's else clause", conditional_stx);
}
if (conditional_stx.IsExpression)
{
// Get single conditional expression
var conditional_list = conditional_stx.AsLinkedList <Value>();
// Check arguments count, should be 2 for each condition
var size = conditional_list.Count;
if (size != 2)
{
throw SchemeError.ArityError("cond", "arity mismatch", 2, size, conditional_list, conditional_stx);
}
// Now get condition and it's expression
var var = conditional_list[0].AsSyntax();
var val = conditional_list[1].AsSyntax();
if (var.IsIdentifier && var.AsIdentifier() == Symbol.ELSE)
{
var ast = AstBuilder.ExpandInternal(val, env);
elsecase = ValueLinkedList.FromArguments(new Value(var), new Value(ast));
}
else
{
var cond_ = AstBuilder.ExpandInternal(var, env);
var then_ = AstBuilder.ExpandInternal(val, env);
var single_cond = ValueLinkedList.FromArguments(cond_, then_);
if (allcases == null)
{
allcases = new LinkedList <Value>();
}
allcases.AddLast(new Value(single_cond));
}
}
else
{
throw SchemeError.SyntaxError("cond", "Expected condition's expression list", conditional_stx);
}
curent = curent.Next;
}
return(new AstCondition(stx, keyword, allcases, elsecase));
}