Hi, 1. I'm reading "A Static semantics for Haskell" and trying to code it up. I came across some odd behavior with pattern bindings, and I was wondering if someone could explain or point me in the right direction. Suppose you have the declaration (x,y) = ('a',2) My current code is yielding: x :: Num a => Char y :: Num a => a However, I notice that ghci gives x the type Char, with no constraint, which is what I would expect. It also gives y the type 'Num b => b', so I don't think it is defaulting a to Int here. The weird results from my code stem from rule BIND-PRED in Figure 15 of https://homepages.inf.ed.ac.uk/wadler/papers/staticsemantics/static-semantic... E |- bind ~~> \dicts : theta -> monobinds in bind : (LIE_{encl}, theta => LVE) Here theta = ( Num a ) and LVE = { x :: Char, y :: a }. So, theta => LVE is { x :: Num a => Char, y :: Num a => a } The obvious thing to do is avoid changing a type T to Num a => T if T does not contain a. Also I'm not totally sure if that trick gets to the bottom of the issue. However, the paper doesn't mention define theta => LVE that way. Is there something else I should read on this? 2. If we just chop out predicates which mention variables not in the type ( == ambiguous predicates?) then I'm not totally sure how to create code for this. I would imagine that we have something like tup dn = ('a', fromInteger dn 2) x = case (tup dn) of (x,y) -> x y dn case (tup dn) of (x,y) -> y In this case its not clear where to get the `dn` argument of `tup` from, in the definition of `x`. Can we pass in `undefined`? Should we do something else? If anyone can shed light on this, I would be grateful :-) -BenRI