[Haskell] Nested guards?
gundberg at dtek.chalmers.se
Tue Dec 4 18:16:26 EST 2007
Have you looked at the proposed view patterns? It seems like it would
cover the case you gave here. I don't know if there's work being done in
this area though.
> Lately I have been using pattern guards more than usual and I find
> that occasionally I need to nest them (i.e., I have alternatives with
> a common prefix). This seems to happen when I need to do some
> preliminary checking, followed by some decision making. Here is an
> server text
> | Just xs <- parse text
> , | "field1" `elem` xs = ... do one thing ...
> | "field2" `elem` xs = ... do something else ...
> server _ = ... invalid request ...
> As far as I can see this should be a fairly simple change to the
> pattern bindings extension. Would anyone else find this a useful
> feature, and if so what syntax should we use?
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