Home Original page

don't NaN & infinities hide FP errors

Gandalf gandalf at geochemsource.com
Wed Nov 17 09:00:05 EST 2004 
>The rest varies across platforms, as explained in this note at the end
>of Python's math module docs:
>
>"""
>The math module consists mostly of thin wrappers around the platform C
>math library functions. Behavior in exceptional cases is loosely
>specified by the C standards, and Python inherits much of its
>math-function error-reporting behavior from the platform C
>implementation. As a result, the specific exceptions raised in error
>cases (and even whether some arguments are considered to be
>exceptional at all) are not defined in any useful cross-platform or
>cross-release way. For example, whether math.log(0) returns -Inf or
>raises ValueError or OverflowError isn't defined, and in cases where
>math.log(0) raises OverflowError, math.log(0L) may raise ValueError
>instead.
>"""
>
I still feel that it would be possible to use some assembly code and 
achieve the same behaviour on all platforms.
It is really not difficult to calculate log on a 387. It can be more 
difficult on a RISC but not impossible.
Why the implementation stuck on the C standards? Okay, maybe it is not 
possible or too difficult to use asm code
on some platforms. But at least Python should try to do the same thing 
when it is possible. It could be an 'option'
to compile low level code for the most popular operating systems. What 
do you think?

   Laci 2.0
More information about the Python-list mailing list