Re: Automatic range creation for class or struct?

[cym13 via Digitalmars-d-learn]

On Wednesday, 10 February 2016 at 00:05:36 UTC, Peka wrote:
Hi!
I have class (or struct) which realises .length() and 
.opIndex(size_t) methods.

It is possible to create from this class some sort of range 
using template from std? (I mean that internal counter, 
.popFront(), .empty() etc methods should be added by template.)

I don't think anything like that exists in phobos but it's not 
hard to pull it out using mixin templates:


mixin template Rangify(T)
if (__traits(hasMember, T, "length")
 && __traits(hasMember, T, "opIndex")) {

    ulong _counter;

    bool empty() {
        return _counter == this.length;
    }

    auto front() {
        return this[_counter];
    }

    auto popFront() {
        _counter++;
    }
}

struct S {
    int[] arr;

    mixin Rangify!S;

    auto length() {
        return arr.length;
    }

    int opIndex(size_t i) {
        return arr[i];
    }
}

void main(string[] args) {
    import std.stdio: writeln;

    auto s = S();
    s.arr = [1, 2, 3];

    foreach (x ; s)
        writeln(x);
}