NAME
Math::SigFigs - do math with correct handling of significant figures
SYNOPSIS
If you only need to use CountSigFigs and FormatSigFigs, use the first
form. If you are going to be doing arithmetic, use the second line.
use Math::SigFigs;
use Math::SigFigs qw(:all);
The following routines do simple counting/formatting:
$n=CountSigFigs($num);
$num=FormatSigFigs($num,$n);
Use the following routines to do arithmetic operations.
$num=addSF($n1,$n2);
$num=subSF($n1,$n2);
$num=multSF($n1,$n2);
$num=divSF($n1,$n2);
DESCRIPTION
In many scientific applications, it is useful (and in some cases
required) to be able to format numbers with a given number of
significant figures, or to do math in such a way as to maintain the
correct number of significant figures. The rules for significant figures
are too complicated to be handled solely using the sprintf function
(unless you happen to be Randal Schwartz :-).
These routines allow you to correctly handle significan figures.
It can count the number of significan figures, format a number to a
given number of significant figures, and do basic arithmetic.
ROUTINES
CountSigFigs
$n=CountSigFigs($N);
This returns the number of significant figures in a number. It
returns () if $N is not a number.
$N $n
----- --
240 2
240. 3
241 3
0240 2
0.03 1
0 0
0.0 0
FormatSigFigs
$str=FormatSigFigs($N,$n)
This returns a string containing $N formatted to $n significant
figures. This will work for all cases except something like "2400"
formatted to 3 significant figures.
$N $n $str
------ -- -------
2400 1 2000
2400 2 2400
2400 3 2400
2400 4 2400.
2400 5 2400.0
141 3 141.
141 2 140
0.039 1 0.04
0.039 2 0.039
9.9 1 10
9.9 2 9.9
9.9 3 9.90
addSF, subSF, multSF, divSF
These routines add/subtract/multiply/divide two numbers while
maintaining the proper number of significant figures.
KNOWN PROBLEMS
Without scientific notation, some numbers are ambiguous
These routines do not work with scientific notation (exponents). As
a result, it is impossible to unambiguously format some numbers. For
example,
$str=FormatSigFigs("2400",3);
will by necessity return the string "2400" which does NOT have 3
significant figures. This is not a bug. It is simply a fundamental
problem with working with significant figures when not using
scientific notation.
AUTHOR
Sullivan Beck (sbeck@cpan.org)