RE: Cube root

[Joel Fritz <JFritz@xxxxxxxxxxxxxxxx>]

The simplest thing would probably be using the C math library functions,
although you could write a small procedure that would use Newton's method or
some similar algorithm to whatever degree of precision you desire.  

I'd have to dig out an old textbook to remember the details of Newton's
method, but with logarithms you find the log of the number, divide it by
three and calculate the log base to the power of the logarithm you just
calculated. The RPG code (after you'd prototyped the log function and
assuming you use base 10 logs) would be:   eval cube_root =
10**(log10(number)/3).  The number whose log you take has to be a float and
the cube root returned will be a float.  

I think the prototype would be something like the following although I
haven't tested it:

 Dlog10            pr             8f   extproc('log10')    
 D number                         8f                       

You'd need to reference binding directory QC2LE to make the C library
functions visible. 

   
-----Original Message-----
From: Walter Hesius [mailto:Walter.Hesius@Village.uunet.be]
Sent: Wednesday, February 14, 2001 1:06 PM
To: RPG400-L@midrange.com
Subject: Cube root


Hi all,

I would like to know a way to calculate the cube root of a number. We are on
V4R4.

Thanx.
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