Re: std.range.interfaces : InputRange moveFront

[Tony via Digitalmars-d-learn]

On Thursday, 30 November 2017 at 06:36:12 UTC, Ali Çehreli wrote:

move is an operation that transfers the state of the source to 
the destination. The front element becomes its .init value and 
its previous values is returned by moveFront().

The important bit is that, the element is *not* copied:

import std.range;

struct S {
    int i;
    bool is_a_copy = false;
    this(this) {
        is_a_copy = true;
    }
}

void main() {
    auto r =  [S(1)];

    auto a = r.front;
    assert(a.is_a_copy);       // yes, a is a copy
    assert(a.i == 1);          // as expected, 1
    assert(r.front.i == 1);    // front is still 1

    auto b = r.moveFront();
    assert(!b.is_a_copy);      // no, b is not a copy
    assert(b.i == 1);          // state is transferred
    assert(r.front.i == 0);    // front is int.init
}


Thanks for the reply. Probably just missing it, but in poking 
around dlang.org (Language Reference and Library Reference) I am 
having trouble finding out about the move(), front() and 
moveFront() functions, as is used here on a dynamic array.