Re: mathlib

[Sean Conner <sean@...>]

It was thus said that the Great Milind Gupta once stated:
> Hi,
>        Once these functions are removed don't we just have to include the
> following code in our Lua program if we use all these and we are good to go?
> 

  [ functions snipped ]

> Would these not be equivalent? 

  They may or may not be.  Floating point math is ... tricky.  The following
covers the topic in depth:

	http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html

There's also an overview of the issues (that might make for some easier
reading) at:

	http://floating-point-gui.de/

  The functions might be perfectly fine for some inputs, and blow up for
other inputs.  I don't know.  I know just enough to know that I don't know
enough.  For instance, this:

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main(void)
{
  printf("%f\n",sin(3.14159265358979323846));
  return EXIT_SUCCESS;
}

prints 0.000000  While this:

[spc]lucy:~>lua
Lua 5.1.5  Copyright (C) 1994-2012 Lua.org, PUC-Rio
> print(math.pi)

prints 1.2246063538224e-16 (math.pi is defined as 3.1415926535898 in Lua
5.1.5).  Even odder, when I change the C code to include the constant as
defined in Lua, I get -0.000000.  You may very well get something different
because of, different CPU, different operating system, different compiler,
etc.  

  -spc (Floating point is messy)