Lars T. Kyllingstad Wrote:
> Paul D. Anderson wrote:
> > I've entered this as a Phobos bug, but wanted to be sure I was
> > understanding this properly (i.e., this is a bug, right?):
> >
> > From the description of the put primitive in std.range:
> >
> > "r.put(e) puts e in the range (in a range-dependent manner) and advances to
> > the popFront position in the range. Successive calls to r.put add elements
> > to the range. put may throw to signal failure."
> >
> > From the example of std.array for the put function:
> >
> > void main()
> > {
> > int[] a = [ 1, 2, 3 ];
> > int[] b = a;
> > a.put(5);
> > assert(a == [ 2, 3 ]);
> > assert(b == [ 5, 2, 3 ]);
> > }
> >
> > So, "putting" 5 into the array a removes the first element in a, and
> > changes the value of the first element of b. I would expect the first
> > assert in the code above to read:
> >
> > assert(a == [ 5, 1, 2, 3 ]);
> >
> > The implementation of std.array.put doesn't make sense:
> >
> > void put(T, E)(ref T[] a, E e) { assert(a.length); a[0] = e; a = a[1 .. $];
> > }
> >
> > It modifies a[0] and then replaces the array with the tail of the array,
> > omitting the first element.
> >
> > It's possible there is some arcane meaning to the word "put" that I'm not
> > aware of, but if it means "insert an element at the front of the range"
> > then std.array.put is wrongly implemented.
> >
> > Paul
>
> I don't think it's a bug, I think it's just that arrays aren't that
> useful as output ranges. It has to be defined that way for it to adhere
> to the range interface conventions. (Think of the array as a file
> instead, then it makes more sense.) You just have to keep a backup
> slice of the entire array so you can access the elements you have put()
> later:
>
> int[] a = [0, 0, 0, 0, 0, 0];
> int[] aSlice = a[];
>
> foreach (i; 0 .. a.length) aSlice.put(i);
>
> assert (a == [0, 1, 2, 3, 4, 5]);
>
> -Lars
Thanks (to all) for the clarification. I was wondering how such a big mistake
could go unnoticed. :-)
I will check into a range re-education camp until my mind is enlightened.
Paul
