Using field selectors in a type constructor

[Graham Klyne]

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


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Graham Klyne
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