Opened 10 years ago

Closed 10 years ago

#829 closed defect (fixed)

atanh branch cut wrong?

Reported by: rtoy Owned by: rme
Priority: normal Milestone:
Component: ANSI CL Compliance Version: trunk
Keywords: Cc:

Description

In ccl 1.6 (32-bit) we have 

1 > (atanh #c(-2d0 -1d-20))
#C(-0.5493061443340549D0 -1.5707963267948966D0)

but 

1 > (atanh #c(-2d0 -0d0))
#C(-0.5493061443340549D0 1.5707963267948966D0)

The spec says that for on the negative real axis less than -1, atanh is continuous with Quadrant III. Since (float-sign -0d0) -> -1d0, both answers should have the same signs and the imaginary part should be negative.

Change History (3)

comment:1 Changed 10 years ago by gb

  • Component changed from IDE to ANSI CL Compliance

comment:2 Changed 10 years ago by rme

  • Owner set to rme

comment:3 Changed 10 years ago by rme

  • Resolution set to fixed
  • Status changed from new to closed

(In [14665]) In ATANH, in the complex argument case, use the formula from the spec exactly. We were using the identity log(x/y) = log(x) - log(y), but this appears to alter the branch cut.

Fixes ticket:829.

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