The following is required to be executed at compile time, and all data is available at compile time: int foo () { foreach (string letter; ["a", "b", "c"]) pragma (msg, letter); return 0; } static const int i = foo(); The expected output when compiling is: a b c The actual result when compiling is: foreach_array.d(5): Error: string expected for message, not 'letter' The issue: static foreach only works for tuples, and I want to use it on an array. This is inconsistent with __traits: the allMembers trait returns an array. If it returned a more obtuse structure, a tuple, then I wouldn't need to use recursion with it; and if static foreach supported arrays, that would make even more code more readable.
Daniel Keep wrote: > Currently, there's no such thing as "static foreach". That the foreach > is unrolled at compile-time is simply a side-effect of the aggregate > being a tuple. > > Walter has already indicated that a true static foreach is planned for 2.x. Now he has a ticket to keep track of it, then :)
This template lets you iterate through a compile-time array as a tuple. Not as good as the real thing, but might be worth having around. template ArrayToTuple( alias T ) { static if( T.length > 1 ) { alias TypeTuple!( T[ 0 ], ArrayToTuple!( T[ 1..$ ] ) ) ArrayToTuple; } else { alias TypeTuple!( T[ 0 ] ) ArrayToTuple; } }
See also bug 4085
Fixed in 2.076 with static foreach.