On Sunday, 4 December 2016 at 13:37:35 UTC, rumbu wrote:
There is nowhere in the documentation where arrays are
advertised as ranges by default.
Huh. It really doesn't seem to say so in the prose. It's shown in
the examples for isInputRange, though:
static assert( isInputRange!(int[]));
static assert( isInputRange!(char[]));
I think that the array range UFCSs must be moved out from the
std.range.primitives and let the library user to decide if
there is a need for range semantics applied to all arrays.
I'm afraid that's not so easy. std.range.primitives.isInputRange
cannot see the range primitives when you import/define them
yourself. You'd have to make isInputRange a mixin template, or
replace the UFCS primitives with a wrapper type, or something
like that. Either way, it'd be a major breaking change.
If you're passionate about this, I suggest you try and find a
solution with an acceptable migration path. Work out all the
annoying little details, and present it as a fleshed-out
proposal. I wouldn't bet on it getting accepted, though. The
current situation may be slightly irritating, but it may be the
lesser evil when compared to breaking everyone's code by messing
with arrays as ranges.
Otherwise, as long as you want array specializations for your
functions, you must decorate all the range specializations with
(isInputRange!T && !isArray!T). And you are compelled to use
"f(T)(T t) if isArray!T" for all your array specializations
instead of "f(T)(T[] x)".
You can also use a "specialization" (in the narrower sense of the
word that the spec uses):
import std.range: isInputRange;
import std.stdio: writeln;
void f(R)(R r) if (isInputRange!R) { writeln("range"); }
void f(A : E[], E)(A a) { writeln("array"); }
void main() { int[] a; f(a); } /* calls the second overload;
prints "array" */
See https://dlang.org/spec/template.html#parameters_specialization
