Library writing - delegates or fp's?

[Derek Parnell]

On Wed, 21 Jun 2006 00:40:15 -0400, Chad J wrote:

> So I have decided to roll my own GUI library, one dedicated to computer 
> games.  But I've run into a bit of an unpleasant design problem - for 
> handling callbacks, how should my library expose function pointers and 
> delegates?
> 
> I suppose I could choose one or the other, but I think it desirable to 
> allow use of both since I don't want to force the user of the library 
> into a particular style or make them use ugly workarounds.  I am 
> currently thinking of a few possible solutions, none of which look very 
> pleasing to me:
> 
> #1:  Force them to use delegates and work around it to do module-level 
> programming.  Example -

It doesn't have to be as complex as that. All you need to do to turn
module-level functions into delegates is to place them inside the module's
constructor or any other function for that matter, including main(). For
example ..

 import std.stdio;
 int delegate(int) increment;
 static this()
 {
    int incr( int a )
    {
         return a + 1;
    }
    increment = &incr;
 }

 void main()
 {
    writefln( increment(1) );
 }

Or if you prefer the new function literal syntax (and not use the module
constructor) ...

 import std.stdio;
 int delegate(int) increment;
 int delegate(int) decrement;

 void Init_Delegates()
 {
    increment = delegate int ( int a )
    {
         return a + 1;
    };


    decrement = delegate int ( int a )
    {
         return a - 1;
    };
 }

 void main()
 {
    Init_Delegates();

    writefln( increment(1) );
    writefln( decrement(1) );
 }


-- 
Derek
(skype: derek.j.parnell)
Melbourne, Australia
"Down with mediocrity!"
21/06/2006 3:18:11 PM