5 Dec
2007
5 Dec
'07
10:40 a.m.
Iavor Diatchki wrote:
Hi, 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 example:
server text | Just xs <- parse text , | "field1" `elem` xs = ... do one thing ... | "field2" `elem` xs = ... do something else ...
server _ = ... invalid request ...
Not having used pattern guards so far, can't you write? server text = case parse text of Just xs | "field1" `elem` xs -> ... do one thing ... | "field2" `elem` xs -> ... do something else ... _ -> ... invalid request ... Christian