Re: Error: this for method name needs to be type S not type MapResult!...

2013-07-03 Thread Michael 

On Saturday, 29 June 2013 at 19:44:00 UTC, Peter Neubauer wrote:

Please explain why this error happens in the following code:

import std.algorithm;

struct S
{
  void foo ()
  {
int f1 (int a) { return conv(a); }
int delegate (int) f2 = conv;

int[] x = [1, 2, 3];
x.map!conv;// ERROR
x.map!f1;  // fine
x.map!f2;  // also fine
  }

  int conv (int a)
  {
return a+1;
  }
}

--- compile output:

/usr/include/d/std/algorithm.d(404): Error: this for conv needs 
to be type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(438): Error: this for conv needs 
to be type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(450): Error: this for conv needs 
to be type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(390): Error: template instance 
std.algorithm.MapResult!(conv, int[]) error instantiating
/home/peter/proggen/goliza.reduced/gtp.d(12):
instantiated from here: map!(int[])
/home/peter/proggen/goliza.reduced/gtp.d(12): Error: template 
instance std.algorithm.map!(conv).map!(int[]) error 
instantiating


---

Thanks,
-Peter


I am not sure if this behavior is intended. Since conv is a 
instance method of S, it has an implicit this which must be of 
type S. I suspect that the map template tries to invoke conv in 
the context of MapResult. I hope template masters can give you a 
more complete explanation though.

Error: this for method name needs to be type S not type MapResult!...

2013-06-29 Thread Peter Neubauer 

Please explain why this error happens in the following code:

import std.algorithm;

struct S
{
  void foo ()
  {
int f1 (int a) { return conv(a); }
int delegate (int) f2 = conv;

int[] x = [1, 2, 3];
x.map!conv;// ERROR
x.map!f1;  // fine
x.map!f2;  // also fine
  }

  int conv (int a)
  {
return a+1;
  }
}

--- compile output:

/usr/include/d/std/algorithm.d(404): Error: this for conv needs to be 
type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(438): Error: this for conv needs to be 
type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(450): Error: this for conv needs to be 
type S not type MapResult!(conv, int[])
/usr/include/d/std/algorithm.d(390): Error: template instance 
std.algorithm.MapResult!(conv, int[]) error instantiating
/home/peter/proggen/goliza.reduced/gtp.d(12):instantiated from 
here: map!(int[])
/home/peter/proggen/goliza.reduced/gtp.d(12): Error: template instance 
std.algorithm.map!(conv).map!(int[]) error instantiating


---

Thanks,
-Peter