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

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");

> 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?

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)