On Mon, Jun 10, 2013 at 2:19 AM, bearophile <bearophileHUGS@lycos.com> wrote:

Timothee Cour:

A)
I'd like to simplify notation of template function declarations involving
only single-argument boolean template constraints as follows:

example:
A1: 'auto myfunction ( isSomeString a, isInputRange b) {...}'

would be rewritten by compiler as:
A2: 'auto myfunction(T0,T1) (T0 a, T1 b) if(isSomeString!T1 a &&
isInputRange!T b) {...}'

IMO, A1 is less verbose and clearer than A2.

Obviously, more complex template constraints would still require the full
syntax, but I'd argue this case is the most common.

See:
http://forum.dlang.org/thread/xaganckgcdkfcmjamogh@forum.dlang.org

ah, great! So I guess it must indeed be a good idea!

from the link:

> If you have two or more types, they must be the same (if you don't want this, you have to use the normal longer syntax)

In what I suggest, the restriction is much weaker so it'd be more generally applicable: for example, 'auto myfunction ( isSomeString a, isInputRange b)' would work in what I suggest but not with the proposal in the link. I don't think it adds any confusion.

Should I draft a DIP?

I'd like to get more feedback before though.

I'll also reply on the above link (CppNow 2013) for your second proposal from cppnow (i think variant does already that).

B)
Secondly, ddoc doesn't generate template constraints or does so very
inconsistently :
in http://dlang.org/phobos/std_algorithm.html we have:
template map(fun...) if (fun.length >= 1);
but all other template constraints are omitted, eg:
void fill(Range, Value)(Range range, Value filler); // template constraint
omitted.
Using the notation proposed in A, wherever applicable, would make documentation clear.

That sounds like a bug report for bugzilla.

just filed: http://d.puremagic.com/issues/show_bug.cgi?id=10325