www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - Create a foreach-able struct? Multi-dimensional even?

reply Heywood Floyd <soul8o8 gmail.com> writes:
Hello!

1) How do I create a struct that I can foreach over?

I get the impression opApply has something do to with this, but I can't find
any documentation on it? (And I'm abroad without my TDPL.)


2) Also, is it possible to do something like this? 

  MyData!(100,100,100) data;
  foreach(x, y, z, ref cell; data){
     cell = x*y*z;
  }

(The idea here is cells are stored in a plain 1-dimensional array behind the
scenes, but iterated as a 3-dimensional array.)


Kind regards
/HF
Aug 25 2011
parent reply Heywood Floyd <soul8o8 gmail.com> writes:
Heywood Floyd Wrote:


 
 Hello!
 
 1) How do I create a struct that I can foreach over?
 
 I get the impression opApply has something do to with this, but I can't find
any documentation on it? (And I'm abroad without my TDPL.)
 
 
 2) Also, is it possible to do something like this? 
 
   MyData!(100,100,100) data;
   foreach(x, y, z, ref cell; data){
      cell = x*y*z;
   }
 
 (The idea here is cells are stored in a plain 1-dimensional array behind the
scenes, but iterated as a 3-dimensional array.)
 
 
 Kind regards
 /HF




Ah, I'm sorry, I found the documentation regarding opApply() now. Typical. (The
site-search didn't seem to work there. Ok..)

Still, is the multi-dimensional part possible?

/HF
Aug 25 2011
parent reply travert phare.normalesup.org (Christophe) writes:
 Still, is the multi-dimensional part possible?



Sure, you have to make an opApply that takes several parameters in its 
delegate.
An exemple:

struct TwoDArray(int nx, int ny)
{
  int[nx][ny] data;

  int opApply(int delegate(ref int i, ref int j, ref int cell)
    {
      foreach (i; 0..nx)
        foreach (j; 0..ny)
          {
            int result = dg(i, j, data[i][j]);
            if (result != 0) return result;
          }
       return 0;
    }
}


// this program prints a multiplication table:
int main()
{
  TwoDArray!(10, 10) data;
  
  foreach(i, j, ref cell; data)
    {
      cell = i * j;
    }

  foreach(i, j, cell; data)
    {
      writefln("%s * %s = %s", i, j, cell);
    }
  return 0;
}
Aug 25 2011
parent Heywood Floyd <soul8o8 gmail.com> writes:
Christophe Wrote:


 Still, is the multi-dimensional part possible?



 Sure, you have to make an opApply that takes several parameters in its 
 delegate.
 An exemple:
 
 struct TwoDArray(int nx, int ny)
 {
   int[nx][ny] data;
 
   int opApply(int delegate(ref int i, ref int j, ref int cell)
     {
       foreach (i; 0..nx)
         foreach (j; 0..ny)
           {
             int result = dg(i, j, data[i][j]);
             if (result != 0) return result;
           }
        return 0;
     }
 }
 
 
 // this program prints a multiplication table:
 int main()
 {
   TwoDArray!(10, 10) data;
   
   foreach(i, j, ref cell; data)
     {
       cell = i * j;
     }
 
   foreach(i, j, cell; data)
     {
       writefln("%s * %s = %s", i, j, cell);
     }
   return 0;
 }
 




Ha! Beautiful, thanks!!
Aug 25 2011