This comes from a Rosettacode entry:
http://rosettacode.org/wiki/First-class_functions#D


import std.stdio, std.math, std.typetuple, std.functional;

enum static sin  = (in real x) pure nothrow => std.math.sin(x),
            asin = (in real x) pure nothrow => std.math.asin(x),
            cos  = (in real x) pure nothrow => std.math.cos(x),
            acos = (in real x) pure nothrow => std.math.acos(x),
            cube = (in real x) pure nothrow => x ^^ 3,
            cbrt = (in real x) /*pure*/ nothrow => std.math.cbrt(x);

void main() {
    alias dir = TypeTuple!(sin,  cos,  cube);
    alias inv = TypeTuple!(asin, acos, cbrt);
    foreach (immutable i, f; dir) {
        writefln("%6.3f %6.3f",
                 compose!(f, inv[i])(0.5),
                 compose!(dir[i], inv[i])(0.5));
    }
}

It prints:

 0.500  0.500
 0.866  0.500
 0.713  0.500

Do you know why there's such difference in the results?

(You can't define a staticZip in D?)

Bye,
bearophile

On 03/14/2014 09:37 AM, bearophile wrote:
> This comes from a Rosettacode entry:
> http://rosettacode.org/wiki/First-class_functions#D
>
>
> import std.stdio, std.math, std.typetuple, std.functional;
>
> enum static sin  = (in real x) pure nothrow => std.math.sin(x),
>              asin = (in real x) pure nothrow => std.math.asin(x),
>              cos  = (in real x) pure nothrow => std.math.cos(x),
>              acos = (in real x) pure nothrow => std.math.acos(x),
>              cube = (in real x) pure nothrow => x ^^ 3,
>              cbrt = (in real x) /*pure*/ nothrow => std.math.cbrt(x);
>
> void main() {
>      alias dir = TypeTuple!(sin,  cos,  cube);
>      alias inv = TypeTuple!(asin, acos, cbrt);
>      foreach (immutable i, f; dir) {
>          writefln("%6.3f %6.3f",
>                   compose!(f, inv[i])(0.5),
>                   compose!(dir[i], inv[i])(0.5));
>      }
> }
>
> It prints:
>
>   0.500  0.500
>   0.866  0.500
>   0.713  0.500

DMD64 D Compiler v2.066-devel-1a70764 prints the following for me:

 0.500  0.500
 0.500  0.500
 0.500  0.500

Maybe a bug fixed? (Or a bug introduced if you are using a more recent one. :) )

>
> Do you know why there's such difference in the results?
>
> (You can't define a staticZip in D?)
>
> Bye,
> bearophile

Ali

On Friday, 14 March 2014 at 16:38:00 UTC, bearophile wrote:
> This comes from a Rosettacode entry:
> http://rosettacode.org/wiki/First-class_functions#D
>
>
> import std.stdio, std.math, std.typetuple, std.functional;
>
> enum static sin  = (in real x) pure nothrow => std.math.sin(x),
>             asin = (in real x) pure nothrow => std.math.asin(x),
>             cos  = (in real x) pure nothrow => std.math.cos(x),
>             acos = (in real x) pure nothrow => std.math.acos(x),
>             cube = (in real x) pure nothrow => x ^^ 3,
>             cbrt = (in real x) /*pure*/ nothrow => std.math.cbrt(x);
>
> void main() {
>     alias dir = TypeTuple!(sin,  cos,  cube);
>     alias inv = TypeTuple!(asin, acos, cbrt);
>     foreach (immutable i, f; dir) {
>         writefln("%6.3f %6.3f",
>                  compose!(f, inv[i])(0.5),
>                  compose!(dir[i], inv[i])(0.5));
>     }
> }
>
> It prints:
>
>  0.500  0.500
>  0.866  0.500
>  0.713  0.500
>
> Do you know why there's such difference in the results?
>

It's a bug, and quite a wierd one at that. See the output from this: http://dpaste.dzfl.pl/1962d61bb185

> (You can't define a staticZip in D?)

You can. I hope it will end up in in std.meta, along with a whole load of other such goodies that I've been working on :)

On Friday, 14 March 2014 at 17:10:53 UTC, John Colvin wrote:
> On Friday, 14 March 2014 at 16:38:00 UTC, bearophile wrote:
>> This comes from a Rosettacode entry:
>> http://rosettacode.org/wiki/First-class_functions#D
>>
>>
>> import std.stdio, std.math, std.typetuple, std.functional;
>>
>> enum static sin  = (in real x) pure nothrow => std.math.sin(x),
>>            asin = (in real x) pure nothrow => std.math.asin(x),
>>            cos  = (in real x) pure nothrow => std.math.cos(x),
>>            acos = (in real x) pure nothrow => std.math.acos(x),
>>            cube = (in real x) pure nothrow => x ^^ 3,
>>            cbrt = (in real x) /*pure*/ nothrow => std.math.cbrt(x);
>>
>> void main() {
>>    alias dir = TypeTuple!(sin,  cos,  cube);
>>    alias inv = TypeTuple!(asin, acos, cbrt);
>>    foreach (immutable i, f; dir) {
>>        writefln("%6.3f %6.3f",
>>                 compose!(f, inv[i])(0.5),
>>                 compose!(dir[i], inv[i])(0.5));
>>    }
>> }
>>
>> It prints:
>>
>> 0.500  0.500
>> 0.866  0.500
>> 0.713  0.500
>>
>> Do you know why there's such difference in the results?
>>
>
> It's a bug, and quite a wierd one at that. See the output from this: http://dpaste.dzfl.pl/1962d61bb185

It's calling sin every time instead of cos or cube

Ali Çehreli:

> DMD64 D Compiler v2.066-devel-1a70764 prints the following for me:
>
>  0.500  0.500
>  0.500  0.500
>  0.500  0.500
>
> Maybe a bug fixed?

Probably yes, thank for all the answers :-)

Bye,
bearophile

John Colvin:

>> (You can't define a staticZip in D?)
>
> You can. I hope it will end up in in std.meta, along with a whole load of other such goodies that I've been working on :)

Is the code for staticZip somewhere online?

Bye,
bearophile