[musl] Floating Point Mathematical Constanst in <math.h> ...

[Damian McGuckin <damianm@esi.com.au>]

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