Inertion sort in perl

vinoth.ree has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Insertion sort in perl by almut (Canon) on Apr 25, 2009 at 11:07 UTC
...because in a string comparison, '2' is not less than '10' (comparison happens character-wise, and '2' is not smaller than '1' (ascii-betically)) `my $n = 10; for my $i (1..$n) { printf "'%s lt %s' is %s\n", $i, $n, $i lt $n ? "true":"false"; } __END__ '1 lt 10' is true '2 lt 10' is false '3 lt 10' is false '4 lt 10' is false '5 lt 10' is false '6 lt 10' is false '7 lt 10' is false '8 lt 10' is false '9 lt 10' is false '10 lt 10' is false` [download] (Tip: change `$n` to 11 in the above snippet and note that `'10 lt 11' is true` in contrast to most others...)	[reply] [d/l] [select]
Re^2: Insertion sort in perl by AnomalousMonk (Archbishop) on Apr 25, 2009 at 13:26 UTC
And as an example of the two different types of ordering (i.e., the default lexicographic-ascending of sort vs. numeric ascending), consider: `>perl -wMstrict -le "my @unsorted = (1, 10, 100, 11, 9, 3, 5, 2); my @lexic_sorted = sort @unsorted; print qq{@lexic_sorted}; my @numeric_sorted = sort { $a <=> $b } @unsorted; print qq{@numeric_sorted}; " 1 10 100 11 2 3 5 9 1 2 3 5 9 10 11 100` [download]	[reply] [d/l]
Re: Inertion sort in perl by Marshall (Canon) on Apr 25, 2009 at 15:44 UTC
First, Perl is not C or FORTAN or ASM. This kind of thing: for ($i=1; $i lt $n; $i++){....} is an extremely "rare duck" in Perl! These i-n (INteger) variables just aren't needed in most cases. Perl uses a variant of QuickSort and for almost all of your sorting, you should too! This is normally faster than SelectSort. Use the power of the language! Re-coding your program, `@a = (8,5,2,4,88,1,5,4,3,2); @a = sort @a; #same as @a = sort{$a <=> $b}@a; #because only digits not alpha/digits print "@a","\n"; #prints: 1 2 2 3 4 4 5 5 8 88` [download]	[reply] [d/l] [select]
Re^2: Inertion sort in perl by Corion (Patriarch) on Apr 25, 2009 at 15:54 UTC
Close, but not entirely true: `>perl -le "print for sort @ARGV" 1 10 2 20 1 10 2 20` [download] But with an explicit comparison, it works: `>perl -le "print for sort{ $a <=> $b } @ARGV" 1 10 2 20 1 2 10 20` [download]	[reply] [d/l] [select]
Re^3: Inertion sort in perl by Marshall (Canon) on Apr 25, 2009 at 17:15 UTC
Yes, we are on the same page here! Thanks for emphasizing the difference between ASCII vs numeric sort order! Corion is completely correct about this...there is a difference. I attach some code that I use for a GUI sort gizmo that doesn't know if it is sorting numbers or alpha-number strings. It uses normal string compare unless both items are strictly numeric and in that case, it uses the "spaceship" operator "<=>" for the compare. `sub alpha_num_cmp { my($a, $b) = @_; if (( $a =~ m/\D/) \|\| ($b =~ m/\D/) ) { #look for a non-digit return ($a cmp $b); #if so, then use string compare } return ($a <=> $b); #otherwise straight numeric comparison }` ~~[download]~~ Ok, a cut-n-paste goof...The above code was one level down in the GUI..Ooops! That code compares "columns" of similar things. Here is more code... #!usr/bin/perl -w use strict; my @a=(8,5,2,4,88,1,10,20,5,4,3,2); my @b = sort @a; print "alpha sort\n"; print "@b\n"; @b = sort {$a<=>$b}@a; print "numeric sort\n"; print "@b\n"; @b = sort alpha_num_cmp @a; print "an any sort\n"; print "@b\n"; sub alpha_num_cmp { if ( ( $a =~ m/\D/) \|\| ($b =~ m/\D/) ) { #look for a non-digit return ($a cmp $b); #if so, then use string compare } return ($a <=> $b); #otherwise straight numeric comparison } __END__ prints: alpha sort 1 10 2 2 20 3 4 4 5 5 8 88 numeric sort 1 2 2 3 4 4 5 5 8 10 20 88 an any sort 1 2 2 3 4 4 5 5 8 10 20 88 [download]	[reply] [d/l] [select]