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Message-ID: <f55390ce-f69-7379-cd88-fd5aef4946e8@esi.com.au>
Date: Sat, 25 Jan 2025 11:24:28 +1100 (AEDT)
From: Damian McGuckin <damianm@....com.au>
To: MUSL <musl@...ts.openwall.com>
Subject: Floating Point Mathematical Constanst in <math.h> ...
This is not specific to MUSL but I figured the knowledge exists in the
list. I was doing a review for a small book I am writing.
As long as one has
defined(_XOPEN_SOURCE) || defined(_GNU_SOURCE) || defined(_BSD_SOURCE)
the constants
M_E
M_LOG2E
M_LOG10E
M_LN2
M_LN10
M_2_SQRT_PI
Has anybody been involved in the global 'need' of these constants, i.e.
how often they appear in people's code such that the names need to be a
global identified as long as one includes both <math.h> and does the
appropriate #defines.
The reason I ask is that I cannot find where any of these is used in
elementary mathematical libraries such as MUSL. Nor can I find the use
of Napier's constant (or Euler's number), i.e. 'e' or M_E, in a few
million lines of engineering and physics software to which I have access.
The average log() or log2() or log10() programs which one might think
could use those logarithm constants instead far more accurate ones
instead.
I would like to say these constants have very little utility in the
average programmer of technical software for engineering or physics
but that might be a little extreme.
Just curious. Sadly, the people who made that decision at Berkeley in the
eighties are quite hard to find these days, most of them enjoying their
well-earned retirements.
Thanks - Damian
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