On Friday, 20 December 2013 at 15:38:56 UTC, Francesco Cattoglio
wrote:
I'm trying to experiment a bit around the iota function.
If I try to impose the following constraits:
Everything works as it should, but according to "D Templates: A
Tutorial" book, you should not use arguments in constraints.
That's news to me.
If I try doing something like:
auto my_iota(B, E)(B begin, E end)
if (is (typeof(++B.init)) && is (typeof(B.init < E.init))) {}
the code stops compiling for integers.
That's normal, because "T.init" is not an lvalue.
If you need an lvalue, we have `std.traits.lvalueOf!T` which you
can use.
That said:
auto my_iota(B, E)(B begin, E end)
if (is (typeof(++begin)) && is (typeof(begin < end))) {}
Seems perfectly legit to me.
On the other hand the code
auto my_iota(B, E)(B begin, E end)
if (is (typeof(++B)) && is (typeof(B < E))) {}
fails to compile for both integers and my defined types.
"B" is a type, so "++B" will always resolve to "__error", unless
you've implemented a static operator (not sure if even legal?).
