this is best code bro

This is actually the best solution instead of using random loops.

fair chance you did not import the "System" namespace (line1)

How did you get the Kata to let you use "Math"
When I tried that it said that "Math does not exist in the current context"

2nd Time I Got Top answer, lets go

read the assertion message, not the line of code:

Invalid result for s = "", part1 = "ac", part2 = "ab"
Expected: false
Actual: true

why the test do_test("", "ac", "ab", false) return false :) isn't the part1 contain "" in its?

God i love haskell

when you want to solve a problem, better way is using the fundamentals of the language not the built-in function.

generic, works for lists and for strings (and probably iterables in general)

That rocks. The lookahead and keeping matches techniques are essentials.