rotate left an array

[Ali Çehreli]

On 10/3/22 17:00, Paul Backus wrote:
 > On Monday, 3 October 2022 at 21:06:36 UTC, Ali Çehreli wrote:
 >> On 10/3/22 13:48, Andrey Zherikov wrote:
 >>> a "rotated view".
 >>
 >> Without indexes:
 >>
 >> import std.range : empty;
 >>
 >> auto rotatedView(R)(R range)
 >> in (!range.empty)
 >> {
 >>     import std.range : chain, front, only, popFront;
 >>     const fr = range.front;
 >>     range.popFront();
 >>     return chain(range, only(fr));
 >> }
 >
 > Tiny nitpick: this should use
 >
 >      const fr = range.save.front;
 >
 > ...to ensure that `fr` is not invaliated or overwritten by the
 > subsequent call to range.popFront (e.g., think of File.byLine here).

Good catch but I think what we want is a copy of the front element, at 
least for InputRanges (.save does not work for File.byLine :/).

What is the generic way of copying an element? I wonder whether we have 
to use isSomeString to take care of all element types.

Ali