On Saturday, 24 January 2015 at 14:53:02 UTC, Andrei Alexandrescu
wrote:
On 1/24/15 3:50 AM, Peter Alexander wrote:
On Friday, 23 January 2015 at 18:22:08 UTC, zeljkog wrote:
On 23.01.15 19:13, Andrei Alexandrescu wrote:
On 1/23/15 10:05 AM, zeljkog wrote:
On 23.01.15 18:48, H. S. Teoh via Digitalmars-d wrote:
I think what he's trying to do is to call a function that
returns a
delegate, and use that delegate to instantiate the filter
template.
AFAIK I've never seen code like this before, and it looks
like the
compiler isn't prepared to handle this.
Yes, I tried to use filter for unique, need closure.
I think there are many applications for this pattern.
Please post a complete snippet then. Thanks! -- Andrei
import std.stdio, std.algorithm;
auto unique(){
bool[int] c;
return (int a){
if (a in c)
return false;
else{
c[a] = true;
return true;
}
};
}
void main()
{
[1, 5, 5, 2, 1, 5, 6, 6].filter!(unique()).writeln;
}
auto f = unique();
[1, 5, 5, 2, 1, 5, 6, 6].filter!(f).writeln; // [1, 5, 2, 6]
Filter needs an alias, and you cannot alias an R-value (it has
no symbol).
Hmmm... we do allow rvalues sometimes (e.g. for strings). I
think we could and should relax the rule to allow rvalues in
this case, too. -- Andrei
I was wrong. R-values work, as long as they are compile time
constants. The problem here is that closures don't yet work in
CTFE (as the error says). Pulling it out as a local variable
works because the alias then binds to the symbol rather than the
value.
