From bug-request at octave dot org Fri Feb  4 13:11:53 2005
Subject: bug in the %g format for sprintf
From: "John W. Eaton" <jwe at bevo dot che dot wisc dot edu>
To: Thorsten Meyer <thorsten dot meyier at gmx dot de>
Cc: bug at octave dot org
Date: Fri, 4 Feb 2005 13:16:13 -0600

On  4-Feb-2005, Thorsten Meyer <thorsten dot meyier at gmx dot de> wrote:

| Bug report for Octave 2.1.64 configured for i386-pc-linux-gnu
| 
| Description:
| -----------
| The %m.ng format string gives the wrong number of digits in sprintf.
| 
| Repeat-By:
| ---------
| 
| GNU Octave, version 2.1.64 (i386-pc-linux-gnu).
| Copyright (C) 2004 John W. Eaton.
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| 
| octave:1> sprintf("%5.0g", 10.23)   <======================
| ans = 1e+01
| octave:2> sprintf("%5.1g", 10.23)   <======================
| ans = 1e+01
| octave:3> sprintf("%5.2g", 10.23)   <======================
| ans =    10
| octave:4> sprintf("%5.3g", 10.23)   <======================
| ans =  10.2
| octave:5> sprintf("%5.4g", 10.23)   <======================
| ans = 10.23
| octave:6> sprintf("%5.5g", 10.23)
| ans = 10.23
| octave:7> sprintf("%5.4f", 10.23)
| ans = 10.2300
| octave:8> sprintf("%5.3f", 10.23)
| ans = 10.230
| octave:9> sprintf("%5.2f", 10.23)
| ans = 10.23
| octave:10> sprintf("%5.1f", 10.23)
| ans =  10.2

I think you are misunderstanding the meaning of the "precision" number
in the "g" format.  In that case, it is the number of significant
figures to display.  This is stated clearly in the "Floating-Point
Conversions" section of the Octave manual and is consistent with the
way C behaves.

jwe



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