On Friday, 22 March 2013 at 07:05:03 UTC, Denis Shelomovskij
wrote:
22.03.2013 1:13, bearophile пишет:
And in foreach:
foreach ((c, ref e); loa)
D already have undocumented[1] front tuple expansion in foreach
over range:
---
import std.algorithm;
import std.stdio;
void main() {
enum s = "this is an example for huffman encoding"d;
foreach (c, n; s.dup.sort().release().group())
writefln("'%s' %s", c, n);
}
---
[1] http://d.puremagic.com/issues/show_bug.cgi?id=7361
I've run in to this a few times and it's very irritating. The
lack of an explicit syntax introduces an ambiguity:
foreach (c, n; s.dup.sort().release().group())
writefln("'%s' %s", c, n);
should c be the index, or should the tuple be unpacked? Currently
the tuple is unpacked. In the general case, there is no easy way
of having n be the tuple and c be the size_t index.
Sure, you could write
foreach (size_t c, n; s.dup.sort().release().group())
writefln("'%s' %s", c, n);
forcing n to be a tuple, which I think should work ( but doesn't,
with a lot of irrelevant error messages:
http://dpaste.dzfl.pl/7589a472 ), but if the first element of the
tuple is also type size_t then you have a true ambiguity.
tldr: If we're going to have tuple unpacking, we need some way of
controlling it.
