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.
