It is a generator btw.

Also, examples show "17 17". It is not clear what this is intended to convey.

The input is 0 [-1]. Actual and expected are not shown; this could be achieved by replacing == by ===. Random tests do not actually guarantee "All numbers in will be positive integers", just that they are non-zero, but generated zeroes will be shown as input.

The string can be converted to a set directly

Yep, the contents of wiki are very different and tests are not passing. Too bad, because this kata is very real-life unlike most of them here.

I'm confused as to why it knows c represents characters in the strings

Fixed. All solutions invalidated I guess. :P

A logic that works for Ruby isn't working for Haskell. There should be consistency across languages. Only 1 default test isn't helping either. We're left with having to attempt trial and error method to fix issues.

I don't know why I am encountering negative indices in Haskell. Shouldn't '>' be explicit. Even if I assume it when it's actually absent, I am not getting the results the tests expect.

i added a return value to the initial code so that it does not throw

proper assertion messages for C

Crystal random tests seem incorrect:

n = 65_u64, p = 10_u64

Expected: 149823132181_u64
     got: 1074082795968_u64

I ran these inputs on python and javascript solutions (including your own, author) and they're indicating my answer is correct.

I just ran this and I'm not getting any errors:

def diagonal(n : UInt64, p : UInt64) : UInt64
  42_u64
end

Issue with the Crystal variant. Getting the below error. Tried removing all my code and still getting it. Seems like something wrong with the tests.

Error in line 1: while requiring "././spec.cr"

in spec.cr:3: while requiring "./fixture"

require "./fixture"
^

in fixture.cr:27: instantiating 'dotest(UInt64, UInt64, UInt64)'

dotest(20_u64, 3_u64, 5985_u64)
^~~~~~

in fixture.cr:3: instantiating 'diagonal(UInt64, UInt64)'

actual = diagonal(n, p)
         ^~~~~~~~

in solution.cr:1: type must be UInt64, not Nil

def diagonal(n : UInt64, p : UInt64) : UInt64