def factorial_ok

bend-collections-laws-math@1.0.0.0 · proofs/math/natural/fact.bend:32

import Base
import bend-collections-laws-math@1.0.0.0/src/math/natural.bend as M
import bend-collections-laws-math@1.0.0.0/proofs/math/natural/lcm.bend as LC
import bend-collections-laws-math@1.0.0.0/spec/math/natural.bend as S

32# factorial(n) == n!
33def factorial_ok(+n: Nat) -> {M.factorial(n) == S.factorial(n) : Nat}:
34  Equal.trans(Nat, M.factorial(n), Nat.mul(1n, S.factorial(n)), S.factorial(n), factorial_go(n, 1n), LC.one_mul(S.factorial(n)))