the source_er’s apprentice: powerful tips & techniques in perl you can start using today

The Source_er’s Apprentice:Powerful Tips & Techniques in Perl you can start using today

Matthew Heusserxndev.com - matt@xndev.comPresented to the West Michigan Perl Mongrels – 8/25/2006

Techniques

… there is a distinct difference between learning to use Perl, and learning to use it well. In my opinion, the best way to learn any language well is to see how others have used it to solve problems

- Some Dude on Amazon.com

Velocity & Pinball skills

Trick #1:Use Parameters

my $new = convert('616-555-1212');print "New Number is $new\n";

sub convert { my $num = shift; $num=~s/^616-5/269-5/g; $num=~s/^616-31/269-31/g; $num=~s/^616-32/269-32/g; return $num;}_

Trick #2:Use Interpolation

my $cash = 50;

my $one = 'The $cash variable is $' . $cash;

my $two = "The \$cash variable is \$$cash";

print $one . "\n";

print "$two \n";

Trick #3:use strict

$str = "Hello, World\n";

print "The value in str is $Str";– BAD!

use strict;my $str = "Hello, World\n";print "The value in str is $Str";

- GOOD!

Trick #4:Become a scope master

use strict;

{

my $name = "joe";

}

print $name;

Trick #5: File Handles

my $f = open_file("TRICK1.TXT");while (<$f>) { print $_;}

sub open_file { my $file = shift; open INFILE, $file

|| die "Could not open $f for read"; return(\*INFILE);}

Trick #6: use croakuse Carp;my $f = open_file("TRICK2.TXT");while (<$f>) { print $_;}

sub open_file { my $file = shift; open INFILE, $file or croak "Could not open $file for read"; return(\*INFILE);}

Trick #7: Handle Exceptions with eval

use Carp;

eval(run());

if ($@) {

print "Died with message $@\n";

}

sub run {

croak "ribbet. ribbet.\n";

}

Trick #8:Use Warnings

use warnings;

my $val;

$val = $val+5;

# or ($val = val + 5);

print "val is $val\n";

Trick #9 To create an error log, re-direct STDERR

trick8.pl 2>err.txt

Trick #10:ArrayRefs as output

my $rasquares = get_squares(16);print "The square of 8 is $rasquares->[8]\n";

sub get_squares { my $num = shift; my @arr; if ($num<1) { croak "get_squares must be a number"; } for (my $idx=0; $idx<$num; $idx++) { $arr[$idx]=$idx*$idx; } return \@arr;}

Trick #11:Avoid C-Style for loops … use foreach

my $rasquares = get_squares(16); my $idx; foreach my $val (@$rasquares) { print "$val\n"; }

sub get_squares { my $num = shift; my @arr; if ($num<1) { croak "get_squares must be a number"; } for (my $idx=0; $idx<$num; $idx++) { $arr[$idx]=$idx*$idx; } return \@arr;}

Trick #12:Use ‘Named Parameters’

my %params = ('height',10,'length',5,'width',3);print volume(%params);

sub volume { my %param = @_; return $param{'height'}*$param{'width'}*$param{'length'}; }

Trick #13:Direct-Attack your RegExps

sub convert { my $num = shift; $num=~s/^616-5/269-5/g; $num=~s/^616-31/269-31/g; $num=~s/^616-32/269-32/g; return $num;}

Trick #14:Use Regular Expression Memory

my %switches;open INFILE, "trick12.txt" or croak "failed to open trick12.txt for read";

while(my $str = <INFILE>) { $str=~ /^\d\d\d-(\d\d\d)-\d\d\d\d/; my $switch = $1; if (!defined($switches{$switch})) { $switches{$switch} = 0; } $switches{$switch}++; print "$switch\n"; }

Trick #15:Create lists of lists with referencesmy $tictac;

my ($idx, $jdx);for ($idx=0; $idx<3; $idx++) { for ($jdx=0; $jdx<3;$jdx++) { $tictac->[$idx]->[$jdx] = "-";

}}

Trick #16:Read a file into an array

chomp(my @data = <INFILE>);

Trick #17:Turn off Warnings when you want

use warnings;my @arr;$arr[0] = 'Some';$arr[1] = 'Values';$arr[3] = 'And some whitespace';$arr[5] = 'To be Concatenated';my $str = join(',', @arr);print $str . "\n";

{ no warnings; my $str = join(',', @arr); print $str . "\n";}

Trick #18:use backticks

my $str = `ls -l`;my @arr = split(/\n/, $str);my $file = $arr[0];$file=~/[-rwxa][-rwxa][-rwxa][-rwxa]\s*(\d*)\s/;my $size = $1;

$file=~/\s200\d\s\s([\w\W]*)/;my $name = $1;print "$name has a size of $size";

Trick #19:‘Sniff’ files with –e and -s

• Or –x, -o, -d, -T,-B, -M …

if (-e 'trick19.pl') {

my $size = -s 'trick19.pl';

print "The size of trick19.pl is $size \n";

}

Trick #20:Avoid manipulating @_ …

… Unless you really want to.

my $total = 6;double($total);print "Total is $total\n";

sub double { $_[0]*=2;}

Trick #21:Named parameters via anonymous hashrefs

print volume({height=>10, length=>5, width=>3});

sub volume { my $rparam = shift; return $rparam->{'height'} *$rparam->{'width'} *$rparam->{'length'}; }

Trick #22:Make your subs type-safe

sub volume { my $rparam = shift; if (!defined($rparam) || ref($rparam) ne 'HASH') { croak('volume function expects a hashref'); } return $rparam->{'height'} *$rparam->{'width'} *$rparam->{'length'}; }

Trick #23 - Decode

• $foo = $str ? 'Y' : 'N';

Trick #24Pull off parameters

• $isTest = $parameters =~ s/^(TEST)//;

Trick #26Use map

@doubled = map { $_*=2} @single;

# Doubles the numerical

#value of a list

Trick #27Use grep

$matches = grep /\$/, @costs;

@us_dollars = grep /\$/, @costs;

Trick #28Learn to use pop, push, shift, unshift# AN ARRAY @coins = ("Quarter", "Dime", "Nickel");

# ADD ELEMENTS push(@coins, "Penny"); print "@coins""; unshift(@coins, "Dollar"); print "@coins"; # REMOVE ELEMENTS pop(@coins); print "@coins";shift(@coins);

Trick #28:Use CPAN / PPM

• www.cpan.org

• Under win32, PPM

Trick #29:Use a tight-feedback-loop environment

• putty / vim

What to do tomorrow

• Go to xndev.com

• Get this powerpoint

• Print it … read it … apply it

What to do next week

• Buy a book

• Experiment with new techniques

What to do next year

• Give a lightning talk

• Speak at PM’s?

• Attend a conference – YAPC::NA is cheap

Bonus: What are your favs?

• Discuss the favorite tips & techniques of the audience.