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Full Discussion: perl: string comparison as numbers
Top Forums UNIX for Advanced & Expert Users perl: string comparison as numbers Post 302119024 by drl on Saturday 26th of May 2007 10:08:05 AM
Old 05-26-2007
Hi.

My take on this is that, as with many things in perl, there is more than one way of doing it. So, you can certainly use function ord as matrixmadhan has shown.

However, like the (Bourne family) shell , there is also an alternate set of relational operators for comparing strings. Here is a (longish) example:
Code:
#!/usr/bin/perl

# @(#) p3       Demonstrate comparison operators.

use warnings;
use strict;

my($first) = "b";
my($last) = "a";

if ( $first == $last ) {
        print " Value $first seems equal to $last with \"==\"\n\n";
}

if ( ord($first) > ord($last) ) {
        print " ords of value $first seems more than $last with \">\"\n\n";
}

if ( $first gt $last ) {
        print " Value $first seems more than $last with \"gt\"\n\n";
}

# Do a few comparisons.

comparison( "aa", "ab");
comparison( "ab", "able");
comparison( "ac", "able");
comparison( "1", "2");
comparison( "11", "2");
comparison( "1 begins this string", "2");

sub comparison {
        my($a,$b) = @_;

        if ( $a le $b ) {
                print " string :$a: is less than string :$b:\n\n";
        } else {
                print " string :$a: is greater than string :$b:\n\n";
        }
}

exit(0);

Which produces:
Code:
% ./p3
Argument "a" isn't numeric in numeric eq (==) at ./p3 line 11.
Argument "b" isn't numeric in numeric eq (==) at ./p3 line 11.
 Value b seems equal to a with "=="

 ords of value b seems more than a with ">"

 Value b seems more than a with "gt"

 string :aa: is less than string :ab:

 string :ab: is less than string :able:

 string :ac: is greater than string :able:

 string :1: is less than string :2:

 string :11: is less than string :2:

 string :1 begins this string: is less than string :2:

For me, this follows the principle of least surprise. See man perlop for details on the operators ... cheers, drl
 

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LEARN ABOUT OSF1

xmstringbytecompare

XmStringByteCompare(3X) 												   XmStringByteCompare(3X)

NAME

       XmStringByteCompare - A compound string function that indicates the results of a byte-by-byte comparison

SYNOPSIS

       #include <Xm/Xm.h>

       Boolean XmStringByteCompare (s1, s2)
	       XmString s1;
	       XmString s2;

DESCRIPTION

       XmStringByteCompare returns a Boolean indicating the results of a byte-by-byte comparison of two compound strings.

       In  general,  if two compound strings are created with the same (char *) string using XmStringCreateLocalized in the same language environ-
       ment, the compound strings compare as equal. If two compound strings are created with the same (char *) string and the same font list  ele-
       ment tag set other than XmFONTLIST_DEFAULT_TAG using XmStringCreate, the strings compare as equal.

       In  some  cases,  once  a  compound string is put into a widget, that string is converted into an internal form to allow faster processing.
       Part of the conversion process strips out unnecessary or redundant information.	If an application then does an XtGetValues to  retrieve  a
       compound  string  from  a widget (specifically, Label and all of its subclasses), it is not guaranteed that the compound string returned is
       byte-for-byte the same as the string given to the widget originally.  Specifies a compound string to be compared with s2 Specifies  a  com-
       pound string to be compared with s1

RETURN VALUE

       Returns True if two compound strings are identical byte-by-byte.

SEE ALSO

       XmStringCreate(3X), XmStringCreateLocalized(3X)

															   XmStringByteCompare(3X)
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