Re: is operator and SortedRange

[ketmar via Digitalmars-d-learn]

On Friday, 11 November 2016 at 11:49:25 UTC, RazvanN wrote:

I am a bit confused about how the is operator works. I have a function which receives an InputRange and a predicate. Now I need to be able to test if the InputRange is actually a SortedRange. I don't care about how the datatypes behind the SortedRange or the predicate, I just need to see if the object is a SortedRange. I have tried the following test:

static if(is(typeof(haystack) == SortedRange!(T, _pred), T, _pred))

where haystack is the InputRange, but the test fails. Is there a way to test if the InputRange is a SortedRange without having to explicitly pass the primitive tupe on top of which the SortedRange is built?

template isSortedRange(T) {
  private import std.range : SortedRange;
  static if (is(T : SortedRange!TT, TT)) {
    enum isSortedRange = true;
  } else {
    enum isSortedRange = false;
  }
}


void main () {
  import std.algorithm : sort;
  int[] a;
  a ~= [1, 6, 3];
  auto b = a.sort;
  pragma(msg, typeof(b));
  pragma(msg, isSortedRange!(typeof(a))); // false
  pragma(msg, isSortedRange!(typeof(b))); // true
}