non-typesafe variadic lazy arguments

[Steven Schveighoffer]

"Steven Schveighoffer" wrote
> "Regan Heath" wrote
>> Does this help:
>>
>> module lazy_any;
>>
>> import std.thread;
>> import std.stdio;
>> import std.c.time;
>> import std.c.string;
>> import std.string;
>>
>> void call(R, U...)(bool condition, R delegate(U) dg, U args)
>> {
>> if (condition)
>> writefln(dg(args));
>> }
>>
>> void main(string[] args)
>> {
>> string bob(int i, string s, float f)
>> {
>> return format("%s, %s, %s", i, s, f);
>> }
>>
>> call(true,  &bob, 1, "test1".idup, 5.2f);
>> call(false, &bob, 2, "test2".idup, 6.3f);
>> call(true,  &bob, 3, "test3".idup, 7.4f);
>> }
>
> I definitely learned something here, but unfortunately, this doesn't solve 
> the problem.  What I want is for the tuple to be converted to delegates 
> just like lazy converts arguments to delegates.
>
> To demonstrate my issue, I think this would still evaluate f:
>
>
> string f(string x, string y)
> {
>  return x ~ y;
> }
>
> call(false, &bob, 1, f("test", "1"), 5.2f);
>
> What I want is a way so that f("test", "1") is not evaluated unless 
> needed.
>
> -Steve
>

However, this does work:

void call(R, U...)(bool condition, R delegate(U) dg, lazy U args)
{
if (condition)
writefln(dg(args));
}

Thanks for the help Regan!!! :)

-Steve