[ python-Feature Requests-1163139 ] expm1 and log1p

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Feature Requests item #1163139, was opened at 2005-03-14 12:24
Message generated for change (Comment added) made by rhettinger
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Category: Python Library
Group: None
>Status: Closed
>Resolution: Rejected
Priority: 5
Submitted By: Keith Briggs (kbriggs)
Assigned to: Nobody/Anonymous (nobody)
Summary: expm1 and log1p

Initial Comment:
Could we please have expm1 and log1p interfaced in the 
math module (where these exist in libm)?   These are 
essential for any serious mathematical applications.
lgamma would be nice too.


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>Comment By: Raymond Hettinger (rhettinger)
Date: 2005-06-02 20:34

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For the reasons mentioned by Tim, closing this RFE.

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Comment By: Tim Peters (tim_one)
Date: 2005-03-14 13:20

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Python code intends to be portable, and the math module 
hasn't yet included any platform-specific functions.

I used to write math libraries for a living, so I know about 
netlib <wink>.  If that's the intended approach to portability , 
it still needs someone to volunteer to do all the non-trivial 
coding, testing, doc, license-hassling, and x-platform config 
work.  Won't be me because I can't make time for it.

Note that you could easily write an extension module 
exposing these functions on _your_ platform (assuming your 
platform C supplies them).

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Comment By: Keith Briggs (kbriggs)
Date: 2005-03-14 12:59

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Is there an objection in principle to including something in the 
math module only if it is found in the system's libm?

If so, a solution would be to use a C implementation of expm1 
when it is not already supplied, for example from fdlibm:
http://www.netlib.org/fdlibm/

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Comment By: Tim Peters (tim_one)
Date: 2005-03-14 12:39

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Hard one, since none of those functions are required by the 
C89 standard, Python doesn't require more than C89, and the 
math module overwhelmingly consists of thin wrappers 
around the platform C's implementations.  When C99 is 
universally available, then it will be easy.  Before then, 
someone would have to volunteer non-trivial work (for 
example, Microsoft's C runtime doesn't supply any of these -- 
it's a x-platform mess).

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