On 12/21/2011 04:54 PM, pompei2 wrote:
Hello.
I want to add the option to iterate objects of my class using foreach. I
need them to be iterable as view-only const and as mutable too. I would
prefer to iterate using the "return a delegate" but if that's not
possible, ranges are fine too. Also, I'd prefer a template-less solution
over a templated one.
This is what I have, which works but has severe code duplication. I
hoped inout would help me here, but I just can't figure it out. I also
gave a try to ranges, but same thing again: I can only get it to work if
I define my things twice.
(syntax highlight for the coming month: http://pastebin.com/TNmWWgsj)
import std.conv, std.stdio;
class Container
{
this(int from, int to)
{
while(from <= to) {
_arr ~= from;
from++;
}
}
// FIXME: severe code duplication for const/nonconst/ref
// and I'm not even trying immutable yet
int delegate(int delegate(ref int)) doIter()
{
writeln("calling non-const");
int doTheIter(int delegate(ref int) dg)
{
int result = 0;
foreach(ref i ; this._arr) {
result = dg(i);
if(result)
break;
}
return result;
}
return &doTheIter;
}
int delegate(int delegate(ref int)) doIter() const
{
writeln("calling const");
int doTheIter(int delegate(ref int) dg)
{
int result = 0;
foreach(i ; this._arr) {
result = dg(i);
if(result)
break;
}
return result;
}
return &doTheIter;
}
int[] _arr;
}
int main(string[] args)
{
Container c = new Container(1, 9);
const Container cc = c;
foreach(ref e ; c.doIter()) {
writeln(e);
e++;
}
foreach(e ; cc.doIter()) {
writeln(e);
}
return 0;
}
Just remove the non-const overload. const member functions work with
mutable, immutable and const receivers.
