Mixin and function template?

[renoX]

Frits van Bommel a écrit :
[cut]
> /** The input must be a format string with embedded "%d{var}"-style
>  *  formatting commands
>  */
> char[] sputf(char[] string) {
>     return "mixin(`std.string.format(` ~ Fmt!(" ~ escape(string) ~ ") ~ 
> `)`)";
> }
> 
> void main(char[][] args) {
>     char[] ret;
>     int x = 2007;
>     
>     ret = mixin(sputf("%d{x}"));
>     
>     writefln("%s", ret);
> }

The difference between your sputf and mine is that mine take a tuple
sputf(A...) instead of a string, is it be possible to have a function 
template take a tuple as an argument that is to say to have something like

char[] sputf(A...)()
{
      return "std.string.format("~Fmt!(A) ~ ");";
}

And still call it like you do above?
It doesn't work when I try to do this, I don't understand why..


> ---
> 
> As short as it is, it took me a while to get it that way.
> This is playing with meta-levels. It mixes in a string containing a 
> mixin expression. It used to be even worse though:
> At first the sputf() function was just a wrapper around an adapted 
> sputf!() template, but all the call() function did was return a mixed-in 
> expression, which was then wrapped into a string that - when mixed in - 
> assigned the second-level mixed-in result to a variable passed by name.
> So it mixed in a string, that mixed in a template, that mixed in an 
> expression -- a three-level mixin. (Careful: multiple meta-levels like 
> that can get really confusing really quick :P)

Yes, I find it very easy to be confused.

> Then I figured, that template mixin (sputfImpl!(), specifically the 
> call() member) must be inlinable ;).
> 
> After adding an escape() function around the format string, the result 
> is what you see above: short but sweet.
> 
> I hope you agree that
> ---
>     ret = mixin(sputf("%d{x}"));
> ---
> is a pretty good syntax :).

I agree, but it's a limited one: you cannot do mixin(sputf("%d",x))
I wanted to syntax to be compatible with the old printf syntax..

Regards,
renoX