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

Magicloud Magiclouds magicloud.magiclouds at gmail.com
Tue Sep 29 03:13:19 EDT 2009

```The properFaction part is correct. So I posted the whole code, since
"isInteger" should accept any reasonable incoming types. Well, in this
one situation, it does not. And I cannot figure out why....

On Tue, Sep 29, 2009 at 3:07 PM, Jimmy Hartzell <jim at shareyourgifts.net> wrote:
> Did you test the properFraction-based code in isolation? If code is
> broken, it's important to figure out which part of it is broken. Also,
> this function is not divided into constituent parts, but is a long unruly
> mess. Dividing it into parts would make it much much more readable, and
> you would then be able to test the parts individually.
>
> Jimmy
>
>> The original code is
>> givenSum num = map (\a ->
>>                       let l = (sqrt \$ fromIntegral (a * a + 2 + 2 *
>> num)) - (fromIntegral a) in
>>                       case properFraction l of
>>                         (_, 0) ->
>>                           True
>>                         _ ->
>>                           False
>>                    ) \$ take num [1..]
>> :t l is (Floating a) => a
>> Well, in ghci
>> *Main> givenSum 10
>> [False,False,False,False,False,False,False,False,False,False]
>>
>> On Tue, Sep 29, 2009 at 2:45 PM, Thomas DuBuisson
>> <thomas.dubuisson at gmail.com> wrote:
>>> On Mon, Sep 28, 2009 at 11:35 PM, Magicloud Magiclouds
>>> <magicloud.magiclouds at gmail.com> wrote:
>>>> It never matches to (_, 0.0)....
>>>> I mean
>>>> case properFraction l of
>>>>  (_, 0) -> l
>>>>  _ -> 0 -- always goes here.
>>>
>>> Odd, it works fine for me.
>>>
>>> f x =
>>>        case properFraction x of
>>>                (_,0) -> True
>>>                _     -> False
>>>
>>>
>>> *Main> f 5
>>> True
>>> *Main> f 5.5
>>> False
>>> *Main> f 4.0
>>> True
>>> *Main> f 4.00000001
>>> False
>>>
>>>
>>> Thomas
>>>
>>
>>
>>
>> --
>> 竹密岂妨流水过
>> 山高哪阻野云飞
>>
>
>
>

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