#4228: atanh (-1) returns NaN instead of -Infinity
---------------------------------+------------------------------------------
Reporter: sbroadhead | Owner:
Type: bug | Status: patch
Priority: normal | Milestone: 6.14.1
Component: Prelude | Version: 6.12.1
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: Incorrect result at runtime
---------------------------------+------------------------------------------
Changes (by norriscm):
* cc: g...@… (added)
* status: new => patch
Comment:
By using a different (but mathematically equivalent) formula for atanh, we
can get the desired behavior without explicitly handling the branch cuts:
{{{
atanh x = 0.5 * log ((1.0+x) / (1.0-x))
}}}
This definition gives atanh 1 == Infinity and atanh -1 == -Infinity. The
attached patch makes the changes in GHC.Float and Data.Complex for the
Float, Double, and Complex a instances.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4228#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
_______________________________________________
Glasgow-haskell-bugs mailing list
[email protected]
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
