[Haskell-cafe] Type error in final generator

Bryan O'Sullivan bos at serpentine.com
Sat Dec 8 19:39:49 EST 2007

Loganathan Lingappan wrote:

> main = do
>         hSetBuffering stdin LineBuffering
>         numList <- processInputs
>         foldr (+) 0 numList

The type of main is understood to be IO (), so it can't return anything.
 You could work around this by rewriting the last line above as follows:

print (foldr (+) 0 numList)

This prints the number, which is presumably what you want, and print has
type IO (), so it works out nicely here.


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