Hi,

I'm looking for a way to do call different functions within a loop, so I won't have to write multiple functions with the same looping mechanism.
I'm not sure if I'm explaing this very well, but this very simple example should clarify:

void foo(int[] arr)
{
	foreach(int val; arr)
	{
		switch(val)
		{
			case 0:
				// call bar(val)
			break;

			case 1:
				// call barOther(val)
			break;

			default:
				throw new Exception("foo");
		}
	}
}


Now, this works, but it doesn't have my preference. I would prefer to use something like this:

void foo(int[] arr, int cmp, callback func(int))
{
	foreach(int val; arr)
	{
		if(val == cmp)
			func(val);
	}
}


How can I do this in D?
Or, is there a better way?

Thanks :)

http://dlang.org/expression.html#FunctionLiteral

Function parameters/variables are declared in D using "ReturnType function(ParameterTypes) symbol". "function" is a keyword here, it can be swapped for "delegate" to get, em, delegates.

In your case something like "void function(int) callback" will do.

On Saturday, 16 February 2013 at 21:03:54 UTC, Dicebot wrote:
> http://dlang.org/expression.html#FunctionLiteral
>
> Function parameters/variables are declared in D using "ReturnType function(ParameterTypes) symbol". "function" is a keyword here, it can be swapped for "delegate" to get, em, delegates.
>
> In your case something like "void function(int) callback" will do.

You mean this?

void foo(int[] arr, int cmp, void function(int) callback)
{
	foreach(int val; arr)
	{
		if(val == cmp)
			callback(val);
	}
}

But how do I then pass bar to foo?

void bar(int val)
{
	writeln(val);
}

This doesn't work:

foo([0,1,2], 1, bar);

On Saturday, February 16, 2013 22:24:19 Lemonfiend wrote:
> On Saturday, 16 February 2013 at 21:03:54 UTC, Dicebot wrote:
> > http://dlang.org/expression.html#FunctionLiteral
> > 
> > Function parameters/variables are declared in D using "ReturnType function(ParameterTypes) symbol". "function" is a keyword here, it can be swapped for "delegate" to get, em, delegates.
> > 
> > In your case something like "void function(int) callback" will
> > do.
> 
> You mean this?
> 
> void foo(int[] arr, int cmp, void function(int) callback)
> {
> 	foreach(int val; arr)
> 	{
> 		if(val == cmp)
> 			callback(val);
> 	}
> }
> 
> But how do I then pass bar to foo?
> 
> void bar(int val)
> {
> 	writeln(val);
> }
> 
> This doesn't work:
> 
> foo([0,1,2], 1, bar);

foo([0, 1, 2], 1, &bar);

should work. void function(int) is a function pointer, so you need to pass it a pointer to a function. bar by itself is attempting to call the function (which won't work due to a lack of arguments). It's discussed in the link to the documentation that Dicebot gave you.

- Jonathan M Davis

On Saturday, 16 February 2013 at 21:31:05 UTC, Jonathan M Davis wrote:
> On Saturday, February 16, 2013 22:24:19 Lemonfiend wrote:
>> On Saturday, 16 February 2013 at 21:03:54 UTC, Dicebot wrote:
>> > http://dlang.org/expression.html#FunctionLiteral
>> > 
>> > Function parameters/variables are declared in D using
>> > "ReturnType function(ParameterTypes) symbol". "function" is a
>> > keyword here, it can be swapped for "delegate" to get, em,
>> > delegates.
>> > 
>> > In your case something like "void function(int) callback" will
>> > do.
>> 
>> You mean this?
>> 
>> void foo(int[] arr, int cmp, void function(int) callback)
>> {
>> 	foreach(int val; arr)
>> 	{
>> 		if(val == cmp)
>> 			callback(val);
>> 	}
>> }
>> 
>> But how do I then pass bar to foo?
>> 
>> void bar(int val)
>> {
>> 	writeln(val);
>> }
>> 
>> This doesn't work:
>> 
>> foo([0,1,2], 1, bar);
>
> foo([0, 1, 2], 1, &bar);
>
> should work. void function(int) is a function pointer, so you need to pass it
> a pointer to a function. bar by itself is attempting to call the function
> (which won't work due to a lack of arguments). It's discussed in the link to
> the documentation that Dicebot gave you.
>
> - Jonathan M Davis

Ah you're right, it does, thanks.
I find the D documentation to generally be very hard to read :(