On Mon, Sep 30, 2013 at 1:06 PM, Alan Buxton <alanbuxton@gmail.com> wrote:

Hi

 

I have something like this – purpose is that I need to drop redundant .0 in a whole number – so to show 1.2345 as 1.2345 and to show 1.0 as 1

 

module Test where

 

niceShow x = if (isInt x) then show (floor x) else show x

 

isInt x = x == fromInteger (floor x)

But the hlint in my vim plugin keeps warning me that

 

test.hs|3 col 38 warning| Defaulting the following constraint(s) to type `Integer'

||            (Integral a0) arising from a use of `floor' at /tmp/test.hs:3:38-42

||            (Show a0) arising from a use of `show' at /tmp/test.hs:3:32-35

|| In the first argument of `show', namely `(floor x)'

|| In the expression: show (floor x)

|| In the expression: if (isInt x) then show (floor x) else show x

 

What does this mean? And what would I need to do in order to prevent this warning?



It looks like you have a type mismatch in `isInt`, floor returns a type in the typeclass Integral (this may or may not be an Integer) but fromInteger demands its input be an Integer. Here are the type sigs:

ghci> :t floor
floor :: (Integral b, RealFrac a) => a -> b
ghci> :t fromIntegral
fromIntegral :: (Integral a, Num b) => a -> b

Changing `fromInteger` to `fromIntegeral` should fix this problem.

It will also help if you write down type signatures explicitly for your two functions.

--
Benjamin Jones