Re: Problem with using std.math: abs and std.complex: abs at the same time

[Simen Kjærås via Digitalmars-d-learn]

On Thursday, 19 September 2019 at 10:25:01 UTC, berni wrote:
On Thursday, 19 September 2019 at 07:26:17 UTC, Simen Kjærås 
wrote:
That does indeed fail to compile, and there's no easy way to 
introduce the module-level abs() function to the scope. Again 
though, MergeOverloads to the rescue:

I'm not sure, if MergeOverloads will be accepted into 
std/math.d. Meanwhile I've created a pull request (#7187), that 
does not handle complex numbers although the algorithm would be 
identical. Maybe handling complex numbers in math.d can be 
added later (or maybe it's better to put this in std/complex.d 
anyway, but then code duplication would be necessary).

You could perfectly well place MergeOverloads inside whatever 
function you make, thus not polluting std.math:

float abs(float f) {
    return f < 0 ? -f : f;
}

unittest {
    import std.complex : complex, cabs = abs;
    template MergeOverloads(T...) {
        static foreach (E; T)
            alias MergeOverloads = E;
    }
    alias abs = MergeOverloads!(cabs, .abs);
    abs(1);
    abs(complex(1,1));
}

(you can also use this to create ridiculous overload sets, since 
MergeOverloads doesn't care if one function is called abs and the 
other dropBackExactly. Please don't do this)

If you want to introduce MergeOverloads to Phobos officially, 
std.math is definitely *not* the place though. :)

I'd probably say std.functional, but I'm not really sure where 
it'd belong. Let's put it in std.exception, since it's an 
exception from D's usual overload rules in functions. :p

I don't think anything in std.math explicitly deals with 
std.complex at this point (some things may handle it 
generically), so it seems std.complex would be the logical place 
for anything that does. Might I ask what specifically you're 
working on?

--
  Simen