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

[Simen Kjærås]

On Wednesday, 18 September 2019 at 13:24:05 UTC, berni wrote:
> On Wednesday, 18 September 2019 at 12:37:28 UTC, Simen Kjærås 
> wrote:
>> How to resolve this, though? The simplest solution is to not 
>> use selective imports:
>>
>>     import std.math;
>>     import std.complex;
>>
>>     writeln(abs(complex(1.0,1.0)));
>>     writeln(abs(1.0));
>
> That works. But: I'm trying to write some code for math.d and 
> when I put this code inside math.d it doesn't work anymore. 
> Also removing "import std.math" or moving it after the other 
> import, did not help.

So what you have is basically this?

import std.stdio;

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

unittest {
     import std.complex : complex, abs;

     auto a = complex(1.0,1.0);
     auto b = 1.0f;

     writeln(abs(a));
     writeln(abs(b));
}

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:

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

unittest {
     import std.complex : complex, cabs = abs;
     alias abs = MergeOverloads!(cabs, .abs);
     abs(1);
     abs(complex(1,1));
}

template MergeOverloads(T...) {
     static foreach (E; T)
         alias MergeOverloads = E;
}

--
   Simen