Why tuples are not ranges?

[Mr.Bingo]

On Thursday, 28 June 2018 at 18:03:09 UTC, Ali Çehreli wrote:
> On 06/28/2018 10:00 AM, Mr.Bingo wrote:
>
> > But is this going to be optimized?
>
> Not our job! :o)
>
> > That is, a tuple is a range!
>
> Similar to the array-slice distinction, tuple is a container, 
> needing its range.
>
> > It is clearly easy to see if a tuple is empty, to get the
> front,
>
> Ok.
>
> > and to
> > pop the front and return a new tuple with n - 1 elements,
> which is
> > really just the tuple(a sliced tuple, say) with the first
> member hidden.
>
> That would be special for tuples because popFront does not 
> return a new range (and definitely not with a new type) but 
> mutates the existing one.
>
> Here is a quick and dirty library solution:
>
> // TODO: Template constraints
> auto rangified(T)(T t) {
>     import std.traits : CommonType;
>     import std.conv : to;
>
>     alias ElementType = CommonType!(T.tupleof);
>
>     struct Range {
>         size_t i;
>
>         bool empty() {
>             return i >= t.length;
>         }
>
>         ElementType front() {
>             final switch (i) {
>                 static foreach (j; 0 .. t.length) {
>                 case j:
>                     return t[j].to!ElementType;
>                 }
>             }
>         }
>
>         void popFront() {
>             ++i;
>         }
>
>         enum length = t.length;
>
>         // TODO: save(), opIndex(), etc.
>     }
>
>     return Range();
> }
>
> unittest {
>     import std.typecons : tuple;
>     import std.stdio : writefln;
>     import std.range : ElementType;
>
>     auto t = tuple(5, 3.5, false);
>     auto r = t.rangified;
>
>     writefln("%s elements of '%s': %(%s, %)",
>              r.length, ElementType!(typeof(r)).stringof, r);
> }
>
> void main() {
> }
>
> Prints
>
> 3 elements of 'double': 5, 3.5, 0
>
> Ali

Thanks, why not add the ability to pass through ranges and arrays 
and add it to phobos?