Bug 5052 – take!(Take!R) should return Take!R, not Take!(Take!R)

From D.learn: On Wed, 13 Oct 2010 18:06:15 +0000, Lars T. Kyllingstad wrote: > On Wed, 13 Oct 2010 16:46:09 +0000, Nick Treleaven wrote: > >> Hi, >> I'm new to D2 ranges but have been following D for some time. I'm >> posting here because I want to check if I'm doing anything wrong before >> filing a bug. >> >> The code below is a test case I made after hitting the problem in real >> code. Basically the pyramid recursive function should print out: [1, 2, >> 3] >> [1, 2] >> [1] >> >> This works fine when calling with an int[] range, but calling with >> SList!int seems to make the compiler hang, eating up memory. >> >> Should I file a bug? >> >> >> import std.stdio; >> import std.range; >> import std.container; >> >> void pyramid(Range)(Range items) >> { >> if (items.empty) >> return; >> writeln(items); >> auto len = walkLength(items); >> auto r = take(items, len - 1); >> pyramid(r); >> } >> >> void main() >> { >> /* array version is fine */ >> int[] arr = [1, 2, 3]; >> pyramid(arr[]); >> >> SList!int list = [1, 2, 3]; >> pyramid(list[]); /* infinite loop with dmd 2.049 */ >> } > > > You are creating an infinite recursion of templates. For an array the > return type of take() is the same array type. For other ranges, the > return type of take() is Take!Range. So when you instantiate pyramid! > Range, it instantiates pyramid!(Take!Range), and then > pyramid!(Take!(Take! Range)), and so on ad infinitum. > > A solution could be to make take!(Take!Range)() just return another > Take! Range. [...]

Fixed in SVN: http://www.dsource.org/projects/phobos/changeset/2102