Re: Function Pointers with Type T

[evilrat via Digitalmars-d-learn]

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 :(

Re: Function Pointers with Type T

[amparacha via Digitalmars-d-learn]

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=comp;

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.

Re: Function Pointers with Type T

[amparacha via Digitalmars-d-learn]

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 :(

Re: Function Pointers with Type T

[amparacha via Digitalmars-d-learn]

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 +
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){

Re: Function Pointers with Type T

[Adam D. Ruppe via Digitalmars-d-learn]

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

Function Pointers with Type T

[amparacha via Digitalmars-d-learn]

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=comp;
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;

}

Re: Function Pointers with Type T

[Adam D. Ruppe via Digitalmars-d-learn]

You can get the code to compile with two changes:

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

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.

Re: Function Pointers with Type T

[ketmar via Digitalmars-d-learn]

On Tue, 16 Sep 2014 01:09:27 +
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){



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