treeowl/lub

information operators: least upper bound (lub) and greatest lower bound (glb)

Lub is an experiment in computing least upper information bounds on (partially defined) functional values. It provides a lub function that is consistent with the unamb operator but has a more liberal precondition. Where unamb requires its arguments to equal when neither is bottom, lub is able to synthesize a value from the partial information contained in both of its arguments, which is useful with non-flat types. For more info on unamb, see the unamb package package on Hackage and on GitHub.

I got inspired for this package after stimulating discussions with Thomas Davie, Russell O'Connor others in the #haskell gang.