Can anyone looks at the following code to fix it.I am having
error when using pointers to functions with argument of type
T.This is a small portion of a program doing a generic quick sort
by passing a comparison function as an argument.

import std.stdio;


int main(){

return 0;
}

bool comp(T)(T left,T right){
//some comparison criteria
return false;
}


void sort(T)(T[]list,int left,int right)
{
int spiltPoint;
bool function(T)(T val1,T val2) ptr=∁
spiltPoint=partition(list,ptr,left,right);	
}

int partition(T)(T[]list,bool function(T)(T val1,T val2)ptr,int
left,int right){

return 2;

}

You can get the code to compile with two changes:

bool function(T)(T val1,T val2) ptr=∁

should be:

bool function(T val1,T val2) ptr=&comp!T;



The function pointer itself isn't a template, so it doesn't need the (T) parameter. Instead, since it is inside a template, you can just use the T from the outside directly.

Moreover, comp has compile time arguments, so you can't take the address of it without forwarding the arguments. So instead of &comp, you use &comp!T - passing the T from the outside to the comparison function too.

and also

int partition(T)(T[]list,bool function(T)(T val1,T val2)ptr,int

should be:

int partition(T)(T[]list,bool function(T val1,T val2)ptr,int


Again because the pointer isn't a new template, it should just use the type T from the outer argument list.

On Tue, 16 Sep 2014 01:09:27 +0000
amparacha via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
wrote:

first change:
  bool function(T)(T val1,T val2) ptr=&comp;
to
  auto ptr = &comp!T;

second change:
  int partition(T)(T[]list,bool function(T)(T val1,T val2)ptr,int left,int right)}
to
  int partition(T)(T[]list,bool function(T val1,T val2)ptr,int left,int right){

On Tuesday, 16 September 2014 at 01:16:14 UTC, Adam D. Ruppe wrote:
>
> bool function(T val1,T val2) ptr=&comp!T;
>
>
> Moreover, comp has compile time arguments, so you can't take the address of it without forwarding the arguments. So instead of &comp, you use &comp!T - passing the T from the outside to the comparison function too.

i wish i knew that back when i needed it, so i could avoid spaghetti mess and not abandon my code :(

Thanks Adam you saved me from alot.Just one more question how can
I compare two arguments of type T.
On Tuesday, 16 September 2014 at 01:16:14 UTC, Adam D. Ruppe
wrote:
> You can get the code to compile with two changes:
>
> bool function(T)(T val1,T val2) ptr=∁
>
> should be:
>
> bool function(T val1,T val2) ptr=&comp!T;
>
>
>
> The function pointer itself isn't a template, so it doesn't need the (T) parameter. Instead, since it is inside a template, you can just use the T from the outside directly.
>
> Moreover, comp has compile time arguments, so you can't take the address of it without forwarding the arguments. So instead of &comp, you use &comp!T - passing the T from the outside to the comparison function too.
>
> and also
>
> int partition(T)(T[]list,bool function(T)(T val1,T val2)ptr,int
>
> should be:
>
> int partition(T)(T[]list,bool function(T val1,T val2)ptr,int
>
>
> Again because the pointer isn't a new template, it should just use the type T from the outer argument list.

Thanks its the right help at right time.
On Tuesday, 16 September 2014 at 09:13:38 UTC, evilrat wrote:
> On Tuesday, 16 September 2014 at 01:16:14 UTC, Adam D. Ruppe wrote:
>>
>> bool function(T val1,T val2) ptr=&comp!T;
>>
>>
>> Moreover, comp has compile time arguments, so you can't take the address of it without forwarding the arguments. So instead of &comp, you use &comp!T - passing the T from the outside to the comparison function too.
>
> i wish i knew that back when i needed it, so i could avoid spaghetti mess and not abandon my code :(

Thankx
On Tuesday, 16 September 2014 at 01:21:57 UTC, ketmar via Digitalmars-d-learn wrote:
> On Tue, 16 Sep 2014 01:09:27 +0000
> amparacha via Digitalmars-d-learn <digitalmars-d-learn@puremagic.com>
> wrote:
>
> first change:
>   bool function(T)(T val1,T val2) ptr=&comp;
> to
>   auto ptr = &comp!T;
>
> second change:
>   int partition(T)(T[]list,bool function(T)(T val1,T val2)ptr,int left,int right)}
> to
>   int partition(T)(T[]list,bool function(T val1,T val2)ptr,int left,int right){

On Tuesday, 16 September 2014 at 17:32:02 UTC, amparacha wrote:
> Thanks Adam you saved me from alot.Just one more question how can
> I compare two arguments of type T.

If you want to compare the values, just use them like regular variables. If you want to compare the types, use:

static if(is(T == R)) { }

or one of the other forms here http://dlang.org/expression.html#IsExpression

For example:

bool typesMatch(T, R)() {
   static if(is(T == R)) return true;
   return false;
}

writeln(typesMatch!(int, float)); // false
writeln(typesMatch!(int, int)); // true