• unknown (12/12) Sep 01 2006 How to implement foreachable template Array class:
• Derek Parnell (27/43) Sep 01 2006 int opApply(int delegate(inout T elem) dg)
• David Medlock (58/101) Sep 05 2006 You can also turn any object into an iterable one with the following mix...

unknown <sphinski netscape.net> writes:

How to implement foreachable template Array class:

class Array(T)
{
   T[] arr;

   public this() {}
   public int count() { return arr.length; }
   public void add(T t) { arr.length = arr.length+1; arr[length-1] = t; }

   opApply() {
     ???
   }
}

I could not find out how to write correct operator opApply.

Derek Parnell <derek nomail.afraid.org> writes:

On Fri, 01 Sep 2006 10:21:57 +0300, unknown wrote:

 How to implement foreachable template Array class:
 
 class Array(T)
 {
    T[] arr;
 
    public this() {}
    public int count() { return arr.length; }
    public void add(T t) { arr.length = arr.length+1; arr[length-1] = t; }
 
    opApply() {
      ???
    }
 }
 
 I could not find out how to write correct operator opApply.

    int opApply(int delegate(inout T elem) dg)
    {   int result = 0;

	for (int i = 0; i < arr.length; i++)
	{
	    result = dg(arr[i]);
	    if (result)
		break;
	}
	return result;
    }
    int opApply(int delegate(inout int idx; inout T elem) dg)
    {   int result = 0;

	for (int i = 0; i < arr.length; i++)
	{
	    result = dg(i, arr[i]);
	    if (result)
		break;
	}
	return result;
    }
-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
1/09/2006 5:28:19 PM

David Medlock <noone nowhere.com> writes:

Derek Parnell wrote:
 On Fri, 01 Sep 2006 10:21:57 +0300, unknown wrote:
 
 
How to implement foreachable template Array class:

class Array(T)
{
   T[] arr;

   public this() {}
   public int count() { return arr.length; }
   public void add(T t) { arr.length = arr.length+1; arr[length-1] = t; }

   opApply() {
     ???
   }
}

I could not find out how to write correct operator opApply.

 
 
     int opApply(int delegate(inout T elem) dg)
     {   int result = 0;
 
 	for (int i = 0; i < arr.length; i++)
 	{
 	    result = dg(arr[i]);
 	    if (result)
 		break;
 	}
 	return result;
     }
     int opApply(int delegate(inout int idx; inout T elem) dg)
     {   int result = 0;
 
 	for (int i = 0; i < arr.length; i++)
 	{
 	    result = dg(i, arr[i]);
 	    if (result)
 		break;
 	}
 	return result;
     }


You can also turn any object into an iterable one with the following mixin:
//use this one for arrays

template applyThis( V, alias var )
{
   public int opApply( int delegate( inout V val ) dg )
   {
     int n = 0;
     foreach( V val; var ) { n = dg(val); if (n) break; }
     return n;
   }
   public int opApply( int delegate( inout int index, inout V val ) dg )
   {
     int n = 0;
     foreach( int index, V val; var ) { n = dg(index,val); if (n) break; }
     return n;
   }
   public V opIndex( int index )
   {
     if ( index<=var.length ) return V.init;
     return var[index];
   }
   public V opIndexAssign( V val, int index )
   {
     if ( var.length<=index ) var.length = index+1;
     return var[index] = val;
   }
}

// Use this one for associative arrays
template applyThis( K, V, alias var )
{
   public int opApply( int delegate( inout K key, inout V val ) dg )
   {
     int n = 0;
     foreach( K key, V val; var ) { n = dg(key,val); if (n) break; }
     return n;
   }

   public V opIndex( K key )
   {
     V* ptr = (key in var);
     if ( ptr is null ) return V.init;
     else return ptr[0];
   }

   public V opIndexAssign( V val, K key )
   {
     return var[key] = val;
   }
}


then say:

class Foo
{
   Bar[]	  array;

   mixin applyThis!(Bar,array);
}


Then you can use it like this:
Foo f = new Foo();
foreach( Bar b; foo ) {...}

-DavidM