[phobos] expand for std.metastrings

[Robert Jacques]

On Tue, 02 Nov 2010 10:03:23 -0400, Andrei Alexandrescu  
<andrei at erdani.com> wrote:

> Thanks, Kenji. All - ideas for a better name? "interp"? Full  
> "interpolate"? Leave it as "expand"?
>
> Andrei

Well, "interpolate" and "interp" have mathematical connotations to me, so  
vote-- for those. Note that functionality of this seems very similar to  
both format and text:

enum int a = 10;
enum string op = "+";
static assert(mixin(expand!q{ ${a*2} ${op} 2 }) == q{ 20 + 2 });
vs.
static assert(Format!(" %s %s 2 ",a*2,op)) == q{ 20 + 2 });
vs.
static assert(text(" ",a*2," ",op," 2 ") == q{ 20 + 2 };

So maybe some variant of format would be appropriate: MixinFormat,  
mFormat, mText, FormatInPlace, etc, though these all seem clunky.  
MixinFormat would make a lot of sense if you could declare a template  
that's always a mixin, and could simply write MixinFormat!q{ ${a*2} ${op}  
2 } instead of mixin(MixinFormat!q{ ${a*2} ${op} 2 }). As this syntax  
comes from perl, we could use that as a prefix: perlFormat / pFormat /  
perlText / pText.

Also, am I missing something with regard to the use cases of expand/inter?  
All the examples given in the documentation seem to be better served by  
either text or Format.