• Justin Whear (18/18) Jul 26 2012 Jonathan M. Davis' recent post about string mixins reminded me of
• Adam D. Ruppe (6/6) Jul 26 2012 It might be useful to do this kind of thing with a filter
• Tobias Pankrath (1/8) Jul 26 2012 template mixins?
• Justin Whear (5/11) Jul 26 2012 No, template mixins can only add declarations: "A Tem­plateMixin takes ...

Justin Whear <justin economicmodeling.com> writes:

Jonathan M. Davis' recent post about string mixins reminded me of 
something I put together a couple of months ago: variable interpolation 
in strings http://dpaste.dzfl.pl/5689d535

Some of the projects I work on have lots of embedded queries which are 
assembled on the fly (not just values but column and table names). Using 
concatenation tends to break the queries up excessively, while using 
format with lots of arguments makes them hard to modify. So I took a page 
from PHP's book and implemented "$foo" style expansion.

My original thought was to allow cool syntax like x!"embedded variable: 
$foo" but template instantiations don't have access to variables from 
instantiation scope (unless you pass them explicitly via alias, of 
course).  Thus the need for string mixins.
The `inContext` version does take a struct or object which constitutes 
the set of available variables.

My ugly parsing code could be replaced (maybe, haven't actually tested 
it) by the nice version(none)'d function which uses regexs if match() was 
available for CTFE.

Justin

"Adam D. Ruppe" <destructionator gmail.com> writes:

It might be useful to do this kind of thing with a filter
function:

string escape(string s) { return s.replace("\n", "\\n"); }

auto foo = "cool\nstuff";
string lol = mixin(x("blah $foo", escape));

assert(lol == "blah cool\\nstuff");

"Tobias Pankrath" <tobias pankrath.net> writes:

 My original thought was to allow cool syntax like x!"embedded 
 variable:
 $foo" but template instantiations don't have access to 
 variables from
 instantiation scope (unless you pass them explicitly via alias, 
 of
 course).

template mixins?

Justin Whear <justin economicmodeling.com> writes:

On Thu, 26 Jul 2012 22:40:25 +0200, Tobias Pankrath wrote:

 My original thought was to allow cool syntax like x!"embedded variable:
 $foo" but template instantiations don't have access to variables from
 instantiation scope (unless you pass them explicitly via alias,
 of course).

 
 template mixins?

No, template mixins can only add declarations: "A Tem­plateMixin takes an 
ar­bi­trary set of de­c­la­ra­tions from the body of a
Tem­plat­eDe­c­la­ra­tion and 
in­serts them into the cur­rent con­text." (http://dlang.org/template-
mixin.html)