It seems incorrect that the following simple function is accepted as a terminating one:
val fnc : (nw: nat) -> (ni: nat) -> (ni_max: nat) -> bool
let rec fnc nw ni ni_max =
match ni with
| ni_max -> false
| _ -> fnc nw (nw + ni) ni_max
Surprisingly, the function does terminate upon evaluating it, for instance, by fnc 0 0 1 and returns false. What am I missing out?
The ni_max in the first branch of the pattern is a fresh binder and has no relation to the parameter ni_max of the function. Your code is equivalent to:
let rec fnc nw ni ni_max =
match ni with
| _ -> false
| _ -> fnc nw (nw + ni) ni_max
which is a function that always returns false.
You probably intended to write
let rec fnc nw ni ni_max =
if ni = ni_max then false
else fnc nw (nw + ni) ni_max
and now the termination checker should complain.
