From: Ian Macdonald <ian@...>
Date: 2002-08-07T08:54:47+09:00
Subject: sort problem

Hi,

I have a file with data like this:

ina1
ina15
inb12
ina9
inc10
inda12
inef14
inab14
inzz8
inzz80
inzz9

etc.

I want to sort it alphabetically on the first part of the string, then
numerically on the second part.

The sorted file should look like this:

ina1
ina9
ina15
inab14
inb12
inc10
inda12
inef14
inzz8
inzz9
inzz80

However, I can't seem to write the Ruby code to do this properly.

Having written the Perl to do this kind of thing many times before, I
set about writing it in Perl and sure enough, the Perl version
works. The Ruby code is so analagous that I just can't see where I'm
going wrong.

Here are the two versions:


Perl
----

undef $/;
@foo = sort { ($c,$d) = ($a =~ /^([a-z]+)([0-9]+)$/);
              ($e,$f) = ($b =~ /^([a-z]+)([0-9]+)$/);
              $c cmp $e or $d <=> $f} split(/\n/, <>);
print join "\n", @foo'


Ruby
----

$/ = nil
foo = gets.split("\n")
r = /^([a-z]+)([0-9]+)$/
foo = foo.sort {|a,b| c,d = r.match(a)[1,2]
                      e,f = r.match(b)[1,2]
                      c <=> e or d.to_i <=> f.to_i}
puts foo


The Ruby version outputs this:

ina1
ina15
ina9
inab14
inb12
inc10
inda12
inef14
inzz80
inzz8
inzz9

which shows that the numeric comparison on the second part of the
string is clearly not working, leading me to suspect that the <=>
operator doesn't work with objects of type Fixnum, but according to
the docs, it gets mixed in from Comparable.

So, what's wrong with the Ruby code? This is Ruby 1.6.7, in case that
matters.

Ian
-- 
Ian Macdonald               | Somewhere in Tenafly, New Jersey, a
ian@caliban.org             | chiropractor is viewing "Leave it to
                            | Beaver"! 
                            | 
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