Hi Monks,

I was kind of puzzled when I found out the following. It is
probably perfectly logical, however ... it puzzled me.

I have the following piece of code (thanks ChOas) which sorts
version-numbers (1.0.a, 1.0.10, 5.5.001, et cetera).

Now I decided that I also needed a similar function that I could
use to compare version-numbers. (Returning -1 when the left
parameter is smaller than the right, returning a 0 when they're
equal and returning a 1 when the left is greater than the right.
This is exactly the same function, not taking the fact that I need
to pass two parameters to it, into account. So I decided to try and
integrate them into one subroutine ...

#!/usr/bin/perl -w

use strict;

sub byVersion;

my ($v1,$v2)=("1.1.1.1","1.1.1.2");

print "$v1 is equal to     $v2\n" if (byVersion($v1,$v2)== 0);
print "$v1 is greater than $v2\n" if (byVersion($v1,$v2)== 1);
print "$v1 is less than    $v2\n" if (byVersion($v1,$v2)==-1);

sub byVersion
{
 my @First=split /\./,$a||shift;
 my @Second=split /\./,$b||shift;
 foreach(0..(($#First>$#Second)?$#Second:$#First))
 {
  next if ($First[$_] eq $Second[$_]);
  return (($First[$_]=~/^\d+$/o)&&($Second[$_]=~/^\d+$/o))?($First[$_]
+<=>$Second[$_]):($First[$_] cmp $Second[$_]);
 }
 return ($#First<=>$#Second);
}

[download]

Doing this results in the following error:

srmpilot@IBP-test$ ./sort.s
Name "main::a" used only once: possible typo at ./sort.s line 20.
Name "main::b" used only once: possible typo at ./sort.s line 21.
1.1.1.1 is less than 1.1.1.2

Which ofcourse is very understandable. I do not use the $a en $b
variables (normally passed on by sort in this example ... I would, however,
in an example in which I needed to actually sort a bunch of versions (see below).

#!/usr/bin/perl -w

use strict;

sub byVersion;

my ($v1,$v2)=("1.1.1.1","1.1.1.2");

#-----------------------------
my @row=(1,2,3,4);
my @nrow=sort byVersion @row;

print "@nrow\n";
#-----------------------------

print "$v1 is equal to     $v2\n" if (byVersion($v1,$v2)== 0);
print "$v1 is greater than $v2\n" if (byVersion($v1,$v2)== 1);
print "$v1 is less than    $v2\n" if (byVersion($v1,$v2)==-1);

sub byVersion
{
 my @First=split /\./,$a||shift;
 my @Second=split /\./,$b||shift;
 foreach(0..(($#First>$#Second)?$#Second:$#First))
 {
  next if ($First[$_] eq $Second[$_]);
  return (($First[$_]=~/^\d+$/o)&&($Second[$_]=~/^\d+$/o))?($First[$_]
+<=>$Second[$_]):($First[$_] cmp $Second[$_]);
 }
 return ($#First<=>$#Second);
}

[download]

Running this results in:

srmpilot@IBP-test$ ./sort.s
1 2 3 4
1.1.1.1 is less than 1.1.1.2

I DO understand the fact that he sorted the row correctly.
Because he used the $a and $b variables ... so, no
error-message appeared. However, I do NOT understand the fact that
the Name "main::a" used only once: possible typo error
didn't occur the second time, while comparing the $v1 and $v2
variables. Because the second time it goes into the byVersion sub
the $a and $b aren't used (as in the above example)

So a)... what happened to the error message ? and b) Is there an easier
way to use byVersion for the two above mentioned (2) purposes ?

I thought of doing something like:

my ($val1,$val2)=("1.1.2","1.1.3");
print "Greater than\n" if ((sort byVersion ($val1,$val2))[-1] eq $val1
+);

[download]

Which works o.k. for this example, however it would give problems
for Smaller than and especially for equals.

Suggestions anyone ? Your help is very much appreciated !

Thanks and Bye, Leon

In reply to Sort and related stuff by leons

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