On Saturday, 16 April 2016 at 02:42:55 UTC, Andrei Alexandrescu
wrote:
So the constraint on chain() is:
Ranges.length > 0 &&
allSatisfy!(isInputRange, staticMap!(Unqual, Ranges)) &&
!is(CommonType!(staticMap!(ElementType, staticMap!(Unqual,
Ranges))) == void)
Noice. Now, an alternative is to express it as a recursive
constraint:
(Ranges.length == 1 && isInputRange!(Unqual!(Ranges[0])))
||
(Ranges.length == 2 &&
isInputRange!(Unqual!(Ranges[0])) &&
isInputRange!(Unqual!(Ranges[1])) &&
!is(CommonType!(ElementType!(Ranges[0]),
ElementType!(Ranges[1])) == void))
|| is(typeof(chain(rs[0 .. $ / 2], chain(rs[$ / 2 .. $]))))
In the latter case there's no need for additional helpers but
the constraint is a bit more bulky.
Pros? Cons? Preferences?
Andrei
Definitely prefer the 1st.
Atila
