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digitalmars.D.learn - How to make a function table?

reply mnar53 <maurizionardo hotmail.it> writes:
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?
Feb 15 2019
parent reply Alex <sascha.orlov gmail.com> writes:
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);
}
´´´
Feb 15 2019
parent mnar53 <maurizionardo hotmail.it> writes:
On Saturday, 16 February 2019 at 06:29:28 UTC, Alex wrote:

 On Saturday, 16 February 2019 at 05:06:55 UTC, mnar53 wrote:

 [...]


 I assume, this would do its job:

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

 [...]


Yes, it works. Thx.
Feb 16 2019