Re: Using field selectors in a type constructor

15 Oct 2003

      At 15:03 15/10/03 +1300, Tom Pledger wrote:
...
If you're willing to introduce *one* more variable in a let or where,
try:
joinVarBindings vb1 vb2
        | vbNull vb1 = vb2
        | vbNull vb2 = vb1
        | otherwise  = this
        where
            this = VarBinding
             { vbMap  = head . filter isJust . flist [ vbMap vb1, vbMap vb2 ]
             , vbEnum = map (\v -> (v,fromJust (vbMap this v))) $
                        boundVars vb1 `union` boundVars vb2
             , vbNull = False
             }
Ah, yes, that's neater.

Thanks.

#g

------------
Graham Klyne
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