• Joel (2/2) Sep 08 2019 I'm trying to understand delegates. Is there any good ways I can
• Max Samukha (3/5) Sep 08 2019 You may want to read this:
• berni (3/5) Sep 08 2019 I wrote a foreach loop using opApply. A side effect of that was,
• =?UTF-8?B?UsOpbXkgTW91w6t6YQ==?= (26/28) Sep 08 2019 I am no compiler implementer, so what is below may contain a lot
• bachmeier (3/5) Sep 09 2019 I think this chapter should give you some useful information:
• Bert (21/23) Sep 10 2019 Simple, don't make it harder than it is.

Joel <joelcnz gmail.com> writes:

I'm trying to understand delegates. Is there any good ways I can 
get a better understanding of them?

Max Samukha <maxsamukha gmail.com> writes:

On Sunday, 8 September 2019 at 10:04:57 UTC, Joel wrote:
 I'm trying to understand delegates. Is there any good ways I 
 can get a better understanding of them?

You may want to read this: 
https://tour.dlang.org/tour/en/basics/delegates

berni <someone something.org> writes:

On Sunday, 8 September 2019 at 10:04:57 UTC, Joel wrote:
 I'm trying to understand delegates. Is there any good ways I 
 can get a better understanding of them?

I wrote a foreach loop using opApply. A side effect of that was, 
that after I managed to do this I understood delegates. :-)

=?UTF-8?B?UsOpbXkgTW91w6t6YQ==?= <remy.moueza gmail.com> writes:

On Sunday, 8 September 2019 at 10:04:57 UTC, Joel wrote:
 I'm trying to understand delegates. Is there any good ways I 
 can get a better understanding of them?


I am no compiler implementer, so what is below may contain a lot 
of inaccuracies and conceptual shortcuts, but here is my view of 
delegates in D.  I hope this helps.

Delegates are fat function pointers.

D arrays are also fat function pointers: they can be implemented 
as a struct with a size_t length and a pointer to the data:

     sruct DArray(T) {
         size_t length;
         T * data;
     }

D delegates can be implemented as a pointer to some context data 
and a function pointer, something similar to D arrays:

     struct DDelegate(Context, Return, Args) {
         Context context;
         Return function(Args) functionPointer;
     }

The context can be:
- a struct value
- a class instance
- some data from a local function frame when the delegate is used 
as a closure.

The compiler replaces a call to the delegate in the source code 
by a call to the function pointer with the right data for runtime.
Something like:

     dg.functionPointer(dg.context, "hello, world");

bachmeier <no spam.net> writes:

On Sunday, 8 September 2019 at 10:04:57 UTC, Joel wrote:
 I'm trying to understand delegates. Is there any good ways I 
 can get a better understanding of them?

I think this chapter should give you some useful information:
http://www.ddili.org/ders/d.en/lambda.html

Bert <Bert gmail.com> writes:

On Sunday, 8 September 2019 at 10:04:57 UTC, Joel wrote:
 I'm trying to understand delegates. Is there any good ways I 
 can get a better understanding of them?

Simple, don't make it harder than it is.

Delegates are basically functions... that is, function 
pointers(they point to some function somewhere in space)... BUT 
they include a "context". The context a scope.


{  // In some scope

    int x;
    d = () { writeln(x); };
}


() { writeln(x); };

is the function defined as a lambda(inline).

It accesses a variable outside of it, that is, in the scope... 
which is called the context.

d is the delegate, it is a function pointer that holds the 
function AND the context pointer.

We can then do

d();

which called/executes the function... the function is called, and 
x can be referenced because d stores the context.

If you do not understand functions, then function pointers, you 
can't understand delegates.