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Not Exactly a Hash Tutorial

by planetscape (Chancellor)
on Jul 01, 2005 at 08:38 UTC ( [id://471590]=perltutorial: print w/replies, xml ) Need Help??

last updated: 2008-12-11

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Quick links:

Code Illustrating Hashes and Related Syntax


Hash Assignment
Hash Element Access
exists ( $hash{$key} )
keys( %hash )
delete ( $hash{key} )
values( %hash )
each( %hash )
Make an "Inverse" Hash
Let's Expand Our Real-World Example...
Visualizing a Hash Structure with FakeHash
A List of Hash Resources
Updates

Some Very Simple Code Illustrating Hashes and Related Syntax

 
#! /usr/local/bin/perl -w
# myHash.pl
# these are very simplistic syntax examples;
# there's much more to know, so see the
# resources below!

use strict;
use warnings;

use Data::Dumper;

[download]
# Hash Assignment
# In this case, a 
#   1  :  1     relationship
# key  => value
my %StateName = (
    AK => 'Alaska',
    AL => 'Alabama',
    AR => 'Arkansas',
    AZ => 'Arizona',
    CA => 'California',
    CO => 'Colorado',
    CT => 'Connecticut',
    DC => 'District Of Columbia',
    DE => 'Delaware',
    FL => 'Florida',
    GA => 'Georgia',
    HI => 'Hawaii',
    IA => 'Iowa',
    ID => 'Idaho',
    IL => 'Illinois',
    IN => 'Indiana',
    KS => 'Kansas',
    KY => 'Kentucky',
    LA => 'Louisiana',
    MA => 'Massachusetts',
    MD => 'Maryland',
    ME => 'Maine',
    MI => 'Michigan',
    MN => 'Minnesota',
    MO => 'Missouri',
    MS => 'Mississippi',
    MT => 'Montana',
    NC => 'North Carolina',
    ND => 'North Dakota',
    NE => 'Nebraska',
    NH => 'New Hampshire',
    NJ => 'New Jersey',
    NM => 'New Mexico',
    NV => 'Nevada',
    NY => 'New York',
    OH => 'Ohio',
    OK => 'Oklahoma',
    OR => 'Oregon',
    PA => 'Pennsylvania',
    RI => 'Rhode Island',
    SC => 'South Carolina',
    SD => 'South Dakota',
    TN => 'Tennessee',
    TX => 'Texas',
    UT => 'Utah',
    VA => 'Virginia',
    VT => 'Vermont',
    WA => 'Washington',
    WI => 'Wisconsin',
    WV => 'West Virginia',
    WY => 'Wyoming'
);


my $href = \%StateName;      # reference to the hash %StateName
print Dumper $href;             # note the order will differ from that
+ above
print "\n";

[download]
# hash element access
my $State = 'SD';                  # planetscape's home state
my $Name = $StateName{$State};
print "planetscape lives in " . $Name . "\.\n\n";

[download]
# exists ( $hash{$key} )
$State = 'QC';               # Quebec, Canada
if (exists($StateName{$State})) {
    print "The abbreviation for $State is " . $StateName{$State} . "\.
+\n\n";
} else {
    print $State . " is not a state! (yet)\n\n";
}

[download]
# keys( %hash )
my $count = keys %StateName;
print "There are $count elements in the hash.\n\n";
foreach $State (keys(%StateName)) {
    print "State abbreviation is '$State'\n";
}
print "\n";

[download]
# delete ( $hash{key} )
delete($StateName{DC});      # DC is not actually a state,
                             # it's a postal abbreviation

[download]
# values( %hash )
$count = values %StateName;  # $count is one less since we deleted DC
print "There are $count elements in the hash.\n\n";
foreach $State (values(%StateName)) {
    print "State name is '$State'\n";
}
print "\n";

[download]
# each( %hash )
while (my($key,$value)=each(%StateName)) {     # there's lots more to 
+know
    print "key='$key', value='$value'\n";     # about "each" - see the
                                                              # resour
+ces below!
}
print "\n";

[download]
# make an inverse hash
my %StateAbbreviation = reverse %StateName;

# exists ( $hash{$key} )
$State = 'Quebec';           # QC
if (exists($StateAbbreviation{$State})) {
    print "The abbreviation for $State is " . $StateAbbreviation{$Stat
+e} . "\.\n\n";
} else {
    print $State . " is not a state! (yet)\n\n";
}
print "\n";

[download]
# let's expand our real-world example from a hash of States
# to a hash of postal abbreviations (not exhaustive)
my %PostalCode = %StateName;    # copy %StateName to %PostalCode
$PostalCode{AS} = 'American Samoa';
$PostalCode{DC} = 'District of Columbia';
$PostalCode{FM} = 'Federated States of Micronesia';
$PostalCode{GU} = 'Guam';
$PostalCode{MH} = 'Marshall Islands';
$PostalCode{MP} = 'Northern Mariana Islands';
$PostalCode{PW} = 'Palau';
$PostalCode{PR} = 'Puerto Rico';
$PostalCode{VI} = 'Virgin Islands';
$PostalCode{PW} = 'Palau';
# many more postal codes and abbreviations for the US and Canada 
# may be found here: http://www.usps.com/ncsc/lookups/usps_abbreviatio
+ns.html
# and here: http://canadaonline.about.com/library/bl/blpabb.htm

foreach my $pc (keys(%PostalCode)) {
    print "PostalCode for '$PostalCode{$pc}' is '$pc'\n";
}

[download]

Visualizing a Hash Structure with FakeHash

FakeHash is a module by Mark-Jason Dominus which was first announced here. I have elaborated slightly on the code presented in order to demonstrate some additional details such as setting drawing parameters. (More info on FakeHash can be found here.)

 

use strict;
use warnings;

use FakeHash;

my %h = (
    When      => 1,
    in        => 2,
    the       => 3,
    course    => 4,
    of        => 5,
    human     => 6,
    events    => 7,
    it        => 8,
    becomes   => 9,
    necessary => 10,
    for       => 11,
    one       => 12,
    people    => 13,
);

open( my $FILEHANDLE, ">FakeHashDrawing.txt" );
my $fake = FakeHash::DrawHash->new;

$fake->draw_param( 'BUCKET', [1.5, 0.75] );
$fake->draw_param( 'KVP' => [2.0, 0.75] );

while ( my ( $key, $value ) = each(%h) ) {
    $fake->store( $key, $value );
}

$fake->draw($FILEHANDLE);
close $FILEHANDLE;

[download]

This code produces the following output:

.PS
boxwid:=1.5; boxht:=0.75
B00: box 
boxwid:=1.5; boxht:=0.75
B01: box with .n at B00.s
circle at B01.c rad 0.1 filled
arrow from B01.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0100: box "becomes" "9" "134720492145(17)"
boxwid:=1.5; boxht:=0.75
B02: box with .n at B01.s
circle at B02.c rad 0.1 filled
arrow from B02.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0200: box "necessary" "10" "164114526854434(2)"
boxwid:=1.5; boxht:=0.75
B03: box with .n at B02.s
circle at B03.c rad 0.1 filled
arrow from B03.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0300: box "human" "6" "131651875(3)"
boxwid:=1.5; boxht:=0.75
B04: box with .n at B03.s
boxwid:=1.5; boxht:=0.75
B05: box with .n at B04.s
boxwid:=1.5; boxht:=0.75
B06: box with .n at B05.s
circle at B06.c rad 0.1 filled
arrow from B06.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0600: box "in" "2" "3686(6)"
boxwid:=2; boxht:=0.75
N0601: box "people" "13" "4647902198(22)"
boxwid:=2; boxht:=0.75
N0602: box "course" "4" "4135697990(6)"
boxwid:=1.5; boxht:=0.75
B07: box with .n at B06.s
boxwid:=1.5; boxht:=0.75
B08: box with .n at B07.s
circle at B08.c rad 0.1 filled
arrow from B08.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0800: box "When" "1" "3344568(24)"
boxwid:=2; boxht:=0.75
N0801: box "one" "12" "128504(24)"
boxwid:=1.5; boxht:=0.75
B09: box with .n at B08.s
circle at B09.c rad 0.1 filled
arrow from B09.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N0900: box "events" "7" "4224378201(25)"
boxwid:=1.5; boxht:=0.75
B10: box with .n at B09.s
circle at B10.c rad 0.1 filled
arrow from B10.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N1000: box "of" "5" "3882(10)"
boxwid:=1.5; boxht:=0.75
B11: box with .n at B10.s
circle at B11.c rad 0.1 filled
arrow from B11.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N1100: box "the" "3" "133915(27)"
boxwid:=1.5; boxht:=0.75
B12: box with .n at B11.s
circle at B12.c rad 0.1 filled
arrow from B12.c right boxwid/2 + 0.2
boxwid:=2; boxht:=0.75
N1200: box "it" "8" "3692(12)"
boxwid:=2; boxht:=0.75
N1201: box "for" "11" "118444(12)"
boxwid:=1.5; boxht:=0.75
B13: box with .n at B12.s
boxwid:=1.5; boxht:=0.75
B14: box with .n at B13.s
boxwid:=1.5; boxht:=0.75
B15: box with .n at B14.s
.PE

[download]

Once you have generated FakeHashDrawing.txt with the above Perl code, you can convert it to PostScript with the following (under Cygwin/*nix):

pic FakeHashDrawing.txt | groff -c -Tps > FakeHashDrawing.ps

View the Output

(I then used Jasc Paint Shop Pro 8 to convert PostScript to PNG for display purposes.)

If you prefer a more "modern" standard such as SVG, you can use a utility such as plotutils' pic2plot to convert from Unix pic format to SVG or any other of a wide variety of formats. For example:

pic2plot -T svg FakeHashDrawing.txt > FakeHashDrawing.svg

Produces (on Cygwin):

<?xml version="1.0" encoding="ISO-8859-1" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 20000303 Stylable//EN"
"http://www.w3.org/TR/2000/03/WD-SVG-20000303/DTD/svg-20000303-stylabl
+e.dtd">
<svg width="8in" height="8in" viewBox="0 0 1 1" preserveAspectRatio="n
+one">
<title>SVG drawing</title>
<desc>This was produced by version 4.1 of GNU libplot, a free library 
+for exporting 2-D vector graphics.</desc>
<rect x="0" y="0" width="1" height="1" style="stroke:none;fill:white;"
+/>
<g transform="translate(0.058854,-0.14453) scale(1,-1) scale(0.11458) 
+" xml:space="preserve" style="stroke:black;stroke-linecap:butt;stroke
+-linejoin:miter;stroke-miterlimit:10.433;stroke-dasharray:none;stroke
+-dashoffset:0;stroke-opacity:1;fill:none;fill-rule:even-odd;fill-opac
+ity:1;font-style:normal;font-variant:normal;font-weight:normal;font-s
+tretch:normal;font-size-adjust:none;letter-spacing:normal;word-spacin
+g:normal;text-anchor:start;">
<rect x="0" y="-0.375" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<rect x="0" y="-1.125" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-0.75" r="0.1" style="stroke-width:0.010267;fill
+:gray;"/>
<line x1="0.75" y1="-0.75" x2="1.7" y2="-0.75" style="stroke-width:0.0
+10267;"/>
<polygon points="1.6,-0.725 1.7,-0.75 1.6,-0.775 " style="stroke-width
+:0.010267;fill:black;"/>
<rect x="1.7" y="-1.125" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-0.56818) scale(1,-1) " style="font-fam
+ily:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;basel
+ine-identifier:centerline;stroke:none;fill:black;">becomes</text>
<text transform="translate(2.7,-0.75) scale(1,-1) " style="font-family
+:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline
+-identifier:centerline;stroke:none;fill:black;">9</text>
<text transform="translate(2.7,-0.93182) scale(1,-1) " style="font-fam
+ily:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;basel
+ine-identifier:centerline;stroke:none;fill:black;">134720492145(17)</
+text>
<rect x="0" y="-1.875" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-1.5" r="0.1" style="stroke-width:0.010267;fill:
+gray;"/>
<line x1="0.75" y1="-1.5" x2="1.7" y2="-1.5" style="stroke-width:0.010
+267;"/>
<polygon points="1.6,-1.475 1.7,-1.5 1.6,-1.525 " style="stroke-width:
+0.010267;fill:black;"/>
<rect x="1.7" y="-1.875" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-1.3182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">necessary</text>
<text transform="translate(2.7,-1.5) scale(1,-1) " style="font-family:
+'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-
+identifier:centerline;stroke:none;fill:black;">10</text>
<text transform="translate(2.7,-1.6818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">164114526854434(2)<
+/text>
<rect x="0" y="-2.625" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-2.25" r="0.1" style="stroke-width:0.010267;fill
+:gray;"/>
<line x1="0.75" y1="-2.25" x2="1.7" y2="-2.25" style="stroke-width:0.0
+10267;"/>
<polygon points="1.6,-2.225 1.7,-2.25 1.6,-2.275 " style="stroke-width
+:0.010267;fill:black;"/>
<rect x="1.7" y="-2.625" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-2.0682) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">human</text>
<text transform="translate(2.7,-2.25) scale(1,-1) " style="font-family
+:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline
+-identifier:centerline;stroke:none;fill:black;">6</text>
<text transform="translate(2.7,-2.4318) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">131651875(3)</text>
<rect x="0" y="-3.375" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<rect x="0" y="-4.125" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<rect x="0" y="-4.875" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-4.5" r="0.1" style="stroke-width:0.010267;fill:
+gray;"/>
<line x1="0.75" y1="-4.5" x2="1.7" y2="-4.5" style="stroke-width:0.010
+267;"/>
<polygon points="1.6,-4.475 1.7,-4.5 1.6,-4.525 " style="stroke-width:
+0.010267;fill:black;"/>
<rect x="1.7" y="-4.875" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-4.3182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">in</text>
<text transform="translate(2.7,-4.5) scale(1,-1) " style="font-family:
+'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-
+identifier:centerline;stroke:none;fill:black;">2</text>
<text transform="translate(2.7,-4.6818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">3686(6)</text>
<rect x="3.7" y="-4.875" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(4.7,-4.3182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">people</text>
<text transform="translate(4.7,-4.5) scale(1,-1) " style="font-family:
+'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-
+identifier:centerline;stroke:none;fill:black;">13</text>
<text transform="translate(4.7,-4.6818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">4647902198(22)</tex
+t>
<rect x="5.7" y="-4.875" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(6.7,-4.3182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">course</text>
<text transform="translate(6.7,-4.5) scale(1,-1) " style="font-family:
+'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-
+identifier:centerline;stroke:none;fill:black;">4</text>
<text transform="translate(6.7,-4.6818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">4135697990(6)</text
+>
<rect x="0" y="-5.625" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<rect x="0" y="-6.375" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-6" r="0.1" style="stroke-width:0.010267;fill:gr
+ay;"/>
<line x1="0.75" y1="-6" x2="1.7" y2="-6" style="stroke-width:0.010267;
+"/>
<polygon points="1.6,-5.975 1.7,-6 1.6,-6.025 " style="stroke-width:0.
+010267;fill:black;"/>
<rect x="1.7" y="-6.375" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-5.8182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">When</text>
<text transform="translate(2.7,-6) scale(1,-1) " style="font-family:'H
+elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id
+entifier:centerline;stroke:none;fill:black;">1</text>
<text transform="translate(2.7,-6.1818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">3344568(24)</text>
<rect x="3.7" y="-6.375" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(4.7,-5.8182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">one</text>
<text transform="translate(4.7,-6) scale(1,-1) " style="font-family:'H
+elvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-id
+entifier:centerline;stroke:none;fill:black;">12</text>
<text transform="translate(4.7,-6.1818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">128504(24)</text>
<rect x="0" y="-7.125" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-6.75" r="0.1" style="stroke-width:0.010267;fill
+:gray;"/>
<line x1="0.75" y1="-6.75" x2="1.7" y2="-6.75" style="stroke-width:0.0
+10267;"/>
<polygon points="1.6,-6.725 1.7,-6.75 1.6,-6.775 " style="stroke-width
+:0.010267;fill:black;"/>
<rect x="1.7" y="-7.125" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-6.5682) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">events</text>
<text transform="translate(2.7,-6.75) scale(1,-1) " style="font-family
+:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline
+-identifier:centerline;stroke:none;fill:black;">7</text>
<text transform="translate(2.7,-6.9318) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">4224378201(25)</tex
+t>
<rect x="0" y="-7.875" width="1.5" height="0.75" style="stroke-width:0
+.010267;"/>
<circle cx="0.75" cy="-7.5" r="0.1" style="stroke-width:0.010267;fill:
+gray;"/>
<line x1="0.75" y1="-7.5" x2="1.7" y2="-7.5" style="stroke-width:0.010
+267;"/>
<polygon points="1.6,-7.475 1.7,-7.5 1.6,-7.525 " style="stroke-width:
+0.010267;fill:black;"/>
<rect x="1.7" y="-7.875" width="2" height="0.75" style="stroke-width:0
+.010267;"/>
<text transform="translate(2.7,-7.3182) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">of</text>
<text transform="translate(2.7,-7.5) scale(1,-1) " style="font-family:
+'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseline-
+identifier:centerline;stroke:none;fill:black;">5</text>
<text transform="translate(2.7,-7.6818) scale(1,-1) " style="font-fami
+ly:'Helvetica',sans-serif;font-size:0.15152;text-anchor:middle;baseli
+ne-identifier:centerline;stroke:none;fill:black;">3882(10)</text>
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[download]

For more on visualizing complex data structures, please see Re: How can I visualize my complex data structure?

A List of Hash Resources
Online:
offsite:

Chapter 3 in Beginning Perl by Simon Cozens (PDF)

Chapter 5 of Picking Up Perl by Bradley M. Kuhn (PDF)

Section 2.3 in Impatient Perl by Greg London (PDF)

Steve's place - Perl Tutorial, by Steve Cook (archive)

Perl Training Australia's superlative materials:

What is Scalar Context? by Dominus

Understand References Today by Dominus

Hashes, as explained in PerlGuts Illustrated, by Gisle Aas

Perl.com: How Hashes Really Work, by Abhijit Menon-Sen

Effective Perl: Intermediate and Advanced Topics contains a wealth of information, not limited to hashes, but also including several pages on Joseph N. Hall's PErl Graphical Structures (PEGS).

Uri Guttman's tutorial on AUTOVIVIFICATION

PerlMonks Tutorials:

the basic datatypes, three, by root

Hash Keys (strings or numbers?), by robot_tourist

The Uniqueness of hashes, by injunjoel

Multidimensional Arrays, by CharlesClarkson

references, by busunsl

References quick reference, by tye

Object Serialization Basics, by chromatic

PerlMonks Categorized Questions and Answers:

Hashes

Other PerlMonks Nodes:

Extracting array of hashes from data by nysus

how to avoid mis-spelling hash keys?, by Gorilla

Perl Internals: Hashes, by Kozz

help with hashes, by Anonymous Monk

The Bad, the Ugly, and the Good of autovivification, by tlm

the third item on tye's scratchpad is a hash intro

Autovivification trick, by blazar

perldocs:

perlfaq4: Data Manipulation - Manipulating numbers, dates, strings, arrays, hashes, and miscellaneous data issues

perldata

perlref

perlreftut }

perldsc    }Thanks, wfsp!

perllol     }

Google:

Obligatory Google

 

Print:

Chapters 5 and 15 of Learning Perl by Randal L. Schwartz and Tom Phoenix

Pages 10-12 and 76-78 of Programming Perl, 3rd Ed., by Larry Wall, Tom Christiansen, Jon Orwant

Chapter 5 of the Perl Cookbook, 1st Ed., by Tom Christiansen, Nathan Torkington

Update: This is only a beginning. I noticed a lack of material on hashes in the Tutorials section, and thought I could contribute something, even though it might be one step at a time...

Update(s): Thanks to wfsp for pointing out... I forgot the perldocs!

2005-07-02: added perlfaq4, perlref, 125289, 137108, 69927, 224434

2005-07-06: several links per section; too lazy to enumerate

2005-07-07: added QandASection: hashes, tye's scratchpad, and some code

2005-08-07: added info on FakeHash, including code and graphics

2005-09-12: fixed several broken links, brought to my attention by Hue-Bond (Thanks!)

2005-12-18: added link to The Uniqueness of hashes, by injunjoel

2006-03-25: re-arranged code and references in more logical order; added anchors; added pic and SVG output and info on pic2plot

2006-03-26: added link to Object Serialization Basics, by chromatic

2006-08-13: added link to Autovivification trick, by blazar

2008-12-11: fixed several broken links, brought to my attention by pmonk4ever (Thanks!); also fixed a few b0rked tags

 

 

p l a n e t s c a p e

Replies are listed 'Best First'.
Re: Not Exactly a Hash Tutorial
by pmonk4ever (Friar) on Dec 11, 2008 at 21:27 UTC
    planetscape,

    Nice 'Not Exactly a Hash Tutorial' article...good job, hashes are certainly clearer now. It helps to cut and paste your examples and run them.

    The following links I noticed were broken:

    Hashes, as explained in PerlGuts Illustrated, by Gisle Aas

    Perl.com: How Hashes Really Work, by Abhijit Menon-Sen

    Effective Perl: Intermediate and Advanced Topics contains a wealth of information, not limited to hashes, but also including several pages on Joseph N. Hall's PErl Graphical Structures (PEGS)

    I received a 404 error for them...

    Other than that I appreciated all the examples you provided and the links that did work, I downloaded the documents...never know when they will disappear...

    Thanks again! :)

    pmonk4ever

    "No trees were harmed in the creation of this node. However, a rather large number of electrons were somewhat inconvenienced."

[reply]
[reply]
Re: Not Exactly a Hash Tutorial
by pmonk4ever (Friar) on Oct 08, 2009 at 00:28 UTC
    Thanks again, for updating the links on this node!

    Have a great day!

    It doesn't appear these Tutorials get much use, kinda dusty down here, *cough, cough* :>)

    pmonk4ever

    "No trees were harmed in the creation of this node. However, a rather large number of electrons were somewhat inconvenienced."

[reply]

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