# How to make a function table?

Alex sascha.orlov at gmail.com
Sat Feb 16 06:29:28 UTC 2019

```On Saturday, 16 February 2019 at 05:06:55 UTC, mnar53 wrote:
> Absolutely a newbie to D. This code mimics c, but unfortunately
> does not work:
>
>
> import std.typecons;
> import std.math;
>
> alias double function(double) UNARY;
>
>
> UNARY[] FCNS = [sin, cos, tan];
>
>
> double[][] MAP (int idx, double[][] args) nothrow {
>     UNARY f = FCNS[idx];
>     foreach(i; 0 .. args.length)
>         foreach(j; 0 .. args[i].length)
>             args[i][j] = f (args[i][j]);
>     return args;
> }
>
>
> what's wrong with it?

I assume, this would do its job:

´´´
import std.typecons;
import std.math;

alias UNARY = double function(double);

UNARY[] FCNS = [&sin, &cos, &tan];

double[][] MAP (size_t idx, double[][] args) {
UNARY f = FCNS[idx];
foreach(i; 0 .. args.length)
foreach(j; 0 .. args[i].length)
args[i][j] = f (args[i][j]);
return args;
}

void main(){
double[][] args;
args.length = 3;
foreach(ref el; args)
el.length = 3;
import std.random : uniform01, dice;
foreach(l; args)
foreach(ref el; l)
el = uniform01;
import std.range : iota;
args = MAP(dice(FCNS.length.iota), args);
import std.stdio : writeln;
writeln(args);
}
´´´
```