power TypeErrors

[Michael Hudson]

bokr at oz.net (Bengt Richter) writes:

> But this makes wonder about working with complex numbers, where
> name bindings might be to plain real negatives as well as complex
> numbers (as easy to do as binding to integers and floats, which makes
> for the '/' problem) yet you might want the same for
>  >>> a = -4.0+0j
>  >>> b = -4.0
>  >>> a ** 0.5
>  (1.2246063538223773e-016+2j)
>  >>> b ** 0.5
>  Traceback (most recent call last):
>    File "<stdin>", line 1, in ?
>  ValueError: negative number cannot be raised to a fractional power
> 
> It seems like a problem analogous to the true division problem,
> except that fewer people expect complex results.

Does anyone actually use complex numbers in Python?  I guess the
numeric folks might.

complex ** complex is multi-valued, of course.  But so's int ** float,
so I guess people can live with that.

> I wouldn't want complex results all the time, but I can see wanting
> to run that way in a limited context.

It's a bit odd that there's no cmath.pow().

> Which comes down again to whether there should be some kind of general
> mechanism to control such modes of operation within scopes such as
> function bodies or statement suites (indented blocks).

Would be nice, but sounds hard.

Cheers,
M.

-- 
  Premature optimization is the root of all evil.
       -- Donald E. Knuth, Structured Programming with goto Statements