Integer -> Int64 sometimes wrong
Conversion from Integer to Int64 values sometimes
produces the wrong
value. In particular, it seems to fail on
small-magnitude negative
values whose representation is large. E.g.
> (fromIntegral ((2^30 -1 + 2^30) - (2^30 + 2^30 ::
Integer))) :: Data.Int.Int64
4294967295
> (fromIntegral ((2^30 - 2 + 2^30) - (2^30 - 1 + 2^30
:: Integer))) :: Data.Int.Int64
-1
The Haskell-level workaround is to do the conversion as
a non-negative
number then negate if needed:
> let fis (i::Integer) = (fromIntegral (signum i) *
fromIntegral (abs i)) :: Data.Int.Int64
> fis ((2^30 -1 + 2^30) - (2^30 + 2^30 :: Integer))
-1
Trac metadata
Trac field |
Value |
Version |
5.04.2 |
Type |
Bug |
TypeOfFailure |
OtherFailure |
Priority |
normal |
Resolution |
ResolvedDuplicate |
Component |
hslibs/lang |
Test case |
|
Differential revisions |
|
BlockedBy |
|
Related |
|
Blocking |
|
CC |
|
Operating system |
|
Architecture |
|