I'd like to have foreach and inline if in templates:


The tIf doesn't work properly but I'm not sure why


template tuple(args...) { alias tuple = args; }

template tIf(bool cond) { alias tIf = tuple!(); }
template tIf(bool cond, alias T)
{
	static if (cond) alias tIF = T; else alias tIF = tuple!();
}

template tForEach(alias func, args...)
{
	pragma(msg, args);
	static if (args.length == 0)
		alias tForEach = tuple!();
	else
	{
		static assert(is(typeof(func(args[0]))), "tForEach: function not valid for argument : "~typeof(args[0]).stringof);
		pragma(msg, "1"~typeof(args[0]).stringof);
		alias tForEach = tuple!(func(args[0]), tIf!(args.length > 1, tForEach!(func, args[1..$])));
	}
}


e.g.,

writeln(tForEach((string x) => x ~ ";", "a", "b"));

should print a;b;

BTW, it works with static if's, I'm trying to use an inline if to reduce redundant code.... since there is no static ?:.

On Saturday, 27 July 2013 at 17:15:54 UTC, JS wrote:
> BTW, it works with static if's, I'm trying to use an inline if to reduce redundant code.... since there is no static ?:.

I don't really understand, since you didn't really explain *what* you were trying to do before pasting that code, but for what it's worth, there *is* static foreach is supported in D, via typetuples. Once you are inside a static you can evaluate the arg statically.

import std.typetuple, std.stdio;
void main()
{
  foreach(I; TypeTuple!(0, 1, 2))
  {
    static if (I == 1)
      writeln(I);
  }
}

As you can see, this compiles, meaning the if is evaluated at compile time. Does this help you?

I'm currently working on a static Iota. Details here:
http://d.puremagic.com/issues/show_bug.cgi?id=4085

On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
> The tIf doesn't work properly but I'm not sure why
[...]
> template tIf(bool cond, alias T)

Lower case 'f' here, ...

> {
> 	static if (cond) alias tIF = T; else alias tIF = tuple!();

... upper case 'F's here.

On Saturday, 27 July 2013 at 19:06:48 UTC, anonymous wrote:
> On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
>> The tIf doesn't work properly but I'm not sure why
> [...]
>> template tIf(bool cond, alias T)
>
> Lower case 'f' here, ...
>
>> {
>> 	static if (cond) alias tIF = T; else alias tIF = tuple!();
>
> ... upper case 'F's here.

Thanks... I'm glad someone can see the tree's from the forest. (I originally was going to use all caps but changed it at the last minute.

On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
> I'd like to have foreach and inline if in templates:

inline if is available as std.traits.Select

On Sunday, 28 July 2013 at 08:30:17 UTC, QAston wrote:
> On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
>> I'd like to have foreach and inline if in templates:
>
> inline if is available as std.traits.Select

This doesn't work for variadic args...

Something Split!(Cond, targ..., split, fargs) is what I need... where split somehow signals the split between the two.

On Sunday, 28 July 2013 at 08:38:01 UTC, JS wrote:
> On Sunday, 28 July 2013 at 08:30:17 UTC, QAston wrote:
>> On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
>>> I'd like to have foreach and inline if in templates:
>>
>> inline if is available as std.traits.Select
>
> This doesn't work for variadic args...
>
> Something Split!(Cond, targ..., split, fargs) is what I need... where split somehow signals the split between the two.

Obviously I mean Select!

The following works but is somewhat of a hack...

module main;

import std.stdio, std.typetuple;

struct tTupleSplit
{

}

template tIndexOf(T, args...)
{
	static if (staticIndexOf!(T, args) < 0) enum tIndexOf = args.length;
	else enum tIndexOf = staticIndexOf!(T, args);
}
template tMin(alias a, alias b)
{
	static if (a < b) alias tMin = a; else alias tMin = b;
}
template tIf(alias cond, args...)
{
	enum sp = tIndexOf!(tTupleSplit, args);
    static if (cond)
	    alias tIf = args[0..tMin!($,sp)];
	else
		alias tIf = args[tMin!($,sp+1)..$];
}

int main(string[] argv)
{

	alias x = tIf!(false, "a", tTupleSplit, "b");
   writeln(x);
   readln();
   return 0;
}

On Sunday, 28 July 2013 at 08:38:40 UTC, JS wrote:
> On Sunday, 28 July 2013 at 08:38:01 UTC, JS wrote:
>> On Sunday, 28 July 2013 at 08:30:17 UTC, QAston wrote:
>>> On Saturday, 27 July 2013 at 17:14:35 UTC, JS wrote:
>>>> I'd like to have foreach and inline if in templates:
>>>
>>> inline if is available as std.traits.Select
>>
>> This doesn't work for variadic args...
>>
>> Something Split!(Cond, targ..., split, fargs) is what I need... where split somehow signals the split between the two.
>
> Obviously I mean Select!

template Wrap(Stuff ...) {alias unwrap = Stuff;}
Select!(cond, Wrap!targs, Wrap!fargs).unwrap