Shlomi Fish wrote:
in addition to the good advice that Uri gave you - some comments on your code.
On Sun, 4 Dec 2011 07:40:09 -0600
Chris Stinemetz<chrisstinem...@gmail.com> wrote:
I have a program that I am working on improveing. The fist step I have
taken is converting it in using the strict pragma.
Now when this subroutine call is made I get the following compilation error:
Global symbol "$cell" requires explicit package name at ./evdo.pl line 279.
Global symbol "$cell" requires explicit package name at ./evdo.pl line 279.
I understand lexical scope, but am having a hard time figuring out how to
fix this.
Any help is greatly apprciated.
Chris
sub getMarket
{
my $_cell = shift;
my $_mkt = "";
my $mkt = "";
foreach $mkt (keys %marketInfo)
{
This is better written using «foreach my $mkt» instead of «foreach $mkt»
my $start = $marketInfo{$mkt}->{"start"};
You should assign $marketInfo{$mkt} to a variable, or alternatively do:
my ($start, $end) = @{$marketInfo{$mkt}}{qw(start end)};
my $end = $marketInfo{$mkt}->{"end"};
if( $cell>= $start&& $cell<= $end)
{
$_mkt = $mkt;
last;
}
}
This loop can be more succinctly expressed using first from List::Util :
return List::Util::first {
my ($start, $end) = @{$marketInfo{$_}}{qw(start end)};
$cell>= $start&& $cell<= $end;
} keys(%marketInfo);
All that put aside, this lookup has O(N) complexity, and you can reduce it to
O(log(N)) by creating a
sorted array of ranges that you will binary search.
^^^^^^^^^^^^ ^^^^^^^^^^^^^
O( log N ) + O( log N )
Or O( log 2N )
While the added efficiency MAY be faster it adds more complexity and it
depends on the size of N and the algorithms implementing sort and search
as to whether it will actually be faster.
We should forget about small efficiencies, say about 97% of the time:
premature optimization is the root of all evil
-- Donald Knuth
John
--
Any intelligent fool can make things bigger and
more complex... It takes a touch of genius -
and a lot of courage to move in the opposite
direction. -- Albert Einstein
--
To unsubscribe, e-mail: beginners-unsubscr...@perl.org
For additional commands, e-mail: beginners-h...@perl.org
http://learn.perl.org/
