[Haskell-cafe] Detecting numeric overflows

[Ryan Ingram]

Actually, looking at the docs, I'm not sure if case expressions work on
unboxed ints; you may need

addCarry (I# x) (I# y) = case addIntC# x y of (# s, c #) -> (I# s, c /=# 0#)

which is somewhat simpler anyways.

  -- ryan

On Tue, Jul 31, 2012 at 1:56 AM, Ryan Ingram <ryani.spam at gmail.com> wrote:

> Sure, but it's easy to roll your own from those primitives:
>
> {-# LANGUAGE MagicHash, UnboxedTuples #-}
> import GHC.Exts
>
> addCarry :: Int -> Int -> (Int, Bool)
> addCarry (I# x) (I# y) = case addIntC# x y of
>      (# s, c #) -> case c of
>          0# -> (I# s, False)
>          _ -> (I# s, True)
>
> or something along those lines.
>
>   -- ryan
>
>
> On Mon, Jul 30, 2012 at 1:43 PM, Евгений Пермяков <permeakra at gmail.com>wrote:
>
>> On 07/31/2012 12:04 AM, Artyom Kazak wrote:
>>
>>> Евгений Пермяков <permeakra at gmail.com> писал в своём письме Mon, 30 Jul
>>> 2012 09:47:48 +0300:
>>>
>>>  Can someone tell me if there are any primitives, that used to detect
>>>> machine type overflows, in ghc haskell ? I perfectly understand, that I can
>>>> build something based on preconditioning of variables, but this will kill
>>>> any performance, if needed.
>>>>
>>>
>>> In GHC.Prim -- primitives addIntC# and subIntC#:
>>>
>>>  addIntC# :: Int# -> Int# -> (#Int#, Int##)
>>>> Add with carry. First member of result is (wrapped) sum; second member
>>>> is 0 iff no overflow occured.
>>>>
>>>
>>>  subIntC# :: Int# -> Int# -> (#Int#, Int##)
>>>> Subtract with carry. First member of result is (wrapped) difference;
>>>> second member is 0 iff no overflow occured.
>>>>
>>>
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>>>
>> Still no way to detect overflow in *.
>>
>> Strangely enough, I found some relevant descriptions in *.pp in dev
>> branch, so I expect them in 7.6.1. They applies to native-size Word and Int
>> only.
>>
>>
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>
>
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