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From: shaunc@gold.gvg.tek.com (Shaun Case)
Newsgroups: comp.lang.c
Subject: Re: Log Library - How is it done in the library code?
Message-ID: <2063@gold.gvg.tek.com>
Date: 12 Mar 91 19:33:43 GMT
References: <15438@smoke.brl.mil> <1991Mar12.014416.4289@m.cs.uiuc.edu> <1991Mar12.165943.11101@zoo.toronto.edu>
Organization: Grass Valley Group, Grass Valley, CA
Lines: 32

Just as a point of minor interest, you can get the exponent of the log
of a string representation of a positive integer by doing a strlen().
(log base 10, of course.)

Example:

strlen("1") -1 ==   0   log == 0
strlen("10") -1 ==  1   log == 1
.
.
.
strlen("1000000") -1 == 7   log == 7

not being a math weenie, I will venture an unsure guess that the
maximum error using this method is ~1.  If you are doing logs
of small numbers, this is obviously unacceptable.

I don't know if doing a trunc/round on a float, followed by a 
conversion to a string and then a strlen is any faster than 
doing a log, but I thought this might be interesting to someone
anyway.  Kind of neat to see a correlation between a number and
its representation in C.

Now, if we could only use strupr() to calculate sin and cos...
:-)

// Shaun //
-- 
Shaun Case:  shaunc@gold.gvg.tek.com  or  atman%ecst.csuchico.edu@RELAY.CS.NET 
 or Shaun Case of 1:119/666.0 (Fidonet)  or  1@9651 (WWIVnet)
---
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