prop

The Disco standard prop library can be imported with

import prop

Currently, it provides only a single function, holds : Prop -> Bool. The idea of this function is that it will try to tell you for sure whether the given proposition is true or false. If it cannot decide it may simply loop forever. By contrast, using the :test REPL command is guaranteed to stop but it may only try some possible inputs and therefore it may not be able to figure out the correct answer.