• amparacha (22/22) Sep 15 2014 Can anyone looks at the following code to fix it.I am having
• Adam D. Ruppe (17/17) Sep 15 2014 You can get the code to compile with two changes:
• evilrat (4/9) Sep 16 2014 i wish i knew that back when i needed it, so i could avoid
• amparacha (2/14) Sep 16 2014
• amparacha (4/21) Sep 16 2014 Thanks Adam you saved me from alot.Just one more question how can
• Adam D. Ruppe (13/16) Sep 16 2014 If you want to compare the values, just use them like regular
• ketmar via Digitalmars-d-learn (13/13) Sep 15 2014 On Tue, 16 Sep 2014 01:09:27 +0000
• amparacha (3/17) Sep 16 2014 Thankx

"amparacha" <paracham mcmaster.ca> writes:

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;

}

"Adam D. Ruppe" <destructionator gmail.com> writes:

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.

"evilrat" <evilrat666 gmail.com> writes:

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 :(

"amparacha" <paracham mcmaster.ca> writes:

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 :(

"amparacha" <paracham mcmaster.ca> writes:

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.

"Adam D. Ruppe" <destructionator gmail.com> writes:

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

ketmar via Digitalmars-d-learn <digitalmars-d-learn puremagic.com> writes:

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=3D&comp;
to
  auto ptr =3D &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 rig=
ht){

"amparacha" <paracham mcmaster.ca> writes:

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){