On 03/25/2014 11:41 AM, Jim Gibson wrote:
On Mar 25, 2014, at 7:56 AM, shawn wilson <ag4ve...@gmail.com> wrote:
Thanks (y'all). Though, I like this one best I think.
BTW, Jim's isn't exactly correct:
my @keys = qw( foo bar second baz first third );
my %primary = ( second => 1, first => 1, third => 1);
And then the output becomes:
Sorted: first, second, third, bar, baz, foo
Which isn't correct.
I humbly beg to differ. Your specification was to sort ‘first’, ‘second’, or
‘third’ before other keys, and the solution I provided does exactly that,
sorting ‘first’, ‘second’, and ‘third’ in alphabetic order before the other
keys.
The values assigned to the %primary hash are irrelevant and are not used in any
comparison. The existence of the key,value pair in the hash is used to specify
which keys are the primary ones.
If you want to specify what order the primary keys should occur, rather than
simple alphabetic order, then you will have to modify the program:
#!/usr/bin/perl
use strict;
use warnings;
my @keys = qw/foo bar baz first second third/;
my %primary = ( first => 3, second => 2, third => 1); # different values for
each key giving sort order (1, 2, 3, etc.)
my @sorted;
@sorted = sort {
if( $primary{$a} && $primary{$b} ) {
return $primary{$a} <=> $primary{$b};
}elsif( $primary{$a} ) {
return -1;
}elsif( $primary{$b} ) {
return +1;
}else{
return $a cmp $b;
} } @keys;
as a coding style thing, when you have basic flow control in if/else
blocks, you can use statement modifiers and drop the blocks. this will
shorten the code, make it a bit faster (block entry is slow), reduce
indents, and save on braces and pixels (which are VERY costly :).
return $primary{$a} <=> $primary{$b}
if $primary{$a} && $primary{$b} ;
return -1 if $primary{$a} ;
return +1 if $primary{$b} ;
return $a cmp $b;
also if the list is very large, it would be optimal to do this key
ordering conversion one time for each element instead of once per
comparison. see Sort::Maker for how this can be done efficiently.
the simplest way would be to make a hash of all possible keys with their
ordering as the values. then a basic hash lookup is done for each key in
the comparision or the precomputed keys.
uri
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