def Gcd.greatest
import bend-collections-laws-math@1.0.0.0/spec/math/natural.bend as Naturalimport Base
import bend-collections-laws-math@1.0.0.0/src/math/natural.bend as M
140# every common divisor divides the gcd
141def Gcd.greatest(+a: Nat, +b: Nat, +d: Nat, +ka: Nat, +kb: Nat, +ea: {a == Nat.mul(ka, d) : Nat}, +eb: {b == Nat.mul(kb, d) : Nat}) -> Type:
142 dvd(d, M.gcd(a, b))