Limitations of C++ range proposal

[jmh530]

I ran across this blog post on limitations of the C++ range 
proposal [1] and wrote up a simple D version in virtually no time.

https://run.dlang.io/is/y6uk18

import std.range : isInputRange, ElementType;

auto interspersed(T, U)(T x, U y)
     if (isInputRange!T && is(U : ElementType!T))
{
     import std.range : dropBackOne;
     import std.algorithm.iteration : map, joiner;

     return x.map!(a => [a, y]).joiner.dropBackOne;
}

void main()
{
     import std.range : iota;
     import std.array : array;

     auto x = iota(5);
     auto y = interspersed(x, 5);
     assert(y.array == [0, 5, 1, 5, 2, 5, 3, 5, 4, 5]);
}


[1] 
https://www.fluentcpp.com/2019/09/13/the-surprising-limitations-of-c-ranges-beyond-trivial-use-cases/