README.md

Max of two natural numbers

Write a function with the following type:

max_nat : int -> int -> int

such that max_nat a b evaluates to the maximum between a and b, if they are both natural numbers (i.e., greater than or equal to 0). If not, the function must fail.

To make a function fail, use the failwith construct. For example:

let always_fail x = failwith("This function always fails")

The following tests must pass:

assert(max_nat 2 5 = 5);;
assert(max_nat 5 2 = 5);;
assert(try max_nat (-2) 5 |> fun _ -> false with _ -> true);;
assert(try max_nat 2 (-5) |> fun _ -> false with _ -> true);;
assert(try max_nat (-2) (-5) |> fun _ -> false with _ -> true);;

Warning: do not even think of using the built-in max function.