[Haskell-cafe] How to decide if a number is an integer?

[Jimmy Hartzell]

$ ghci
Prelude> let isInteger' l = case properFraction l of { (_,0) -> 1; _ -> 0 }
Prelude> isInteger' 2.0
1
Prelude> isInteger' 1.9
0

Do you really get 1? For what input types/values? Although I would write:
isInteger = (== 0) . snd . properFraction

> It never matches to (_, 0.0)....
> I mean
> case properFraction l of
>   (_, 0) -> l
>   _ -> 0 -- always goes here.
>
> On Tue, Sep 29, 2009 at 2:18 PM, Jimmy Hartzell <jim at shareyourgifts.net>
> wrote:
>> Use properFraction:
>> http://haskell.org/ghc/docs/latest/html/libraries/base/Prelude.html#v%3AproperFraction
>>
>>> Hi,
>>> Â  In other weak-type language, `round i == i` would work. But in
>>> haskell, what should I do? Thanks.
>>> --
>>> 竹密岂妨流水过
>>> 山高哪阻野云飞
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>
>
>
> --
> 竹密岂妨流水过
> 山高哪阻野云飞
>