But isn't the point of this code that you don't need that type signature? If I knew in advance that it was an Integer then I wouldn't need to passs "Integer" in the list. -Alex- On Thu, 29 Apr 2004, Chung-chieh Shan wrote:
On 2004-04-28T23:33:31-0400, S. Alexander Jacobson wrote:
I don't think this works. I just tried it with: main = print $ lookupRead 1 [(1,("Integer","100"))]
This fails for the same reason
print $ read "100"
fails. You need to give a type signature to avoid type-class instance ambiguity:
main = print $ (lookupRead 1 [(1,("Integer","100"))] :: Maybe Integer)
On GHCi 6.2.1, the above yields "Just 100" for me.
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_________________________________________________________________ S. Alexander Jacobson mailto:me@alexjacobson.com tel:917-770-6565 http://alexjacobson.com