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Perl Development (Sample Courseware)
- 1. Perl Development Sample Courseware Created October 2008 © Garth Gilmour 2008
- 3. Introduction to Perl History and Basic Concepts © Garth Gilmour 2008
- 6. Comparing Perl, Python and Ruby © Garth Gilmour 2008 Perl Python Ruby Documentation ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Library Support ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ OO Support ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Power ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Approachability ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Ease of Mastery ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ C / C++ Interop ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Java / .NET Interop ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ Web Frameworks ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦ ♦
- 8. © Garth Gilmour 2008 Scripts Core language features Programs Strict module Subroutines References Applications Best Practises Named Parameters Modules and classes
- 14. © Garth Gilmour 2008 Symbol Table Typeglob $fred = 12; @fred = (12,13,14); %fred = (k1 =>12, k2 => 14); sub fred { return 101; } Name Link fred Others… Type Link $ @ % &
- 16. Using Heredoc Comments © Garth Gilmour 2008 $myvar = << "THE_END"; More than prince of cats, I can tell you. O, he is the courageous captain of compliments. He fights as you sing prick-song, keeps time, distance, and proportion; rests me his minim rest, one, two, and the third in your bosom: the very butcher of a silk button, a duellist, a duellist; a gentleman of the very first house, of the first and second cause: ah, the immortal passado! the punto reverso! the hay! THE_END print "--- START DATA ---", $myvar, "--- END DATA ---";
- 19. Basic Programming The Core Perl Syntax © Garth Gilmour 2008
- 22. Operators Commonly Used in Perl © Garth Gilmour 2008 Description Number Version String Version Addition $var1 + $var2 $var1 . $var2 Equality $var1 == $var2 $var1 eq $va2 Ordered Comparison >, <, <=, >= lt, gt, le, ge Power Of $var1 ** 3 $var1 x 3 Bitwise Comparison &, |, ^ (NB work differently for numbers and strings) Logical &&, ||, ! and, or, not (Lower precedence) Conditional $var1 = $var2 ? 12 : 14; Range 1..4 ‘ D’ .. ‘Z’
- 23. © Garth Gilmour 2008 $num1 = 42; $num2 = "42"; $result = $num1 + $num2; print "adding numbers gives $result", ""x2; $result = $num1 . $num2; print "adding strings gives $result", ""x2; $result = $num2 ** 3; print "42 to the power of 3 is $result", ""x2; $result = $num1 x 3; print "42 concatenated with itself three times is $result", ""x2; if($num1 == $num2) { print '$num1 and $num2 are equal as numbers',""x2; } if($num1 eq $num2) { print '$num1 and $num2 are equal as strings',""x2; }
- 25. © Garth Gilmour 2008 $var1 = "abc"; $var2 = 123; $var3 = ["ab","cd","ef"]; print 'Values are $var1, $var2 and $var3 '; print "Values are $var1, $var2 and $var3 "; $path = `set path`; print "Value of path environment variable is: $path"; Values are $var1, $var2 and $var3 Values are abc, 123 and ARRAY(0x225e28) Value of path environment variable is: PATH=c:dk1.5.0_05in;C:erlitein;C:erlin;c:ubyin;C:INDOWSystem32;C:INDOWS;C:INDOWSystem32bem;
- 27. © Garth Gilmour 2008 $var1 = "0"; # The string "0" counts as false $var2 = ""; # The empty string also counts as false $var3 = "AB"; # Other string values are true $var4 = -12; # Other numerical values are true $var5; # Undefined values are false $var6 = undef(); # Values set to undef are false printTruth('$var1',$var1); printTruth('$var2',$var2); printTruth('$var3',$var3); printTruth('$var4',$var4); printTruth('$var5',$var5); printTruth('$var6',$var6); undef($var4); # Release storage space for var1 so it becomes undefined printTruth('$var4',$var4); sub printTruth { my ($varName,$varValue) = @_; if($varValue) { print "$varName is true"; } else { print "$varName is false"; } }
- 29. Special Scalar Variables © Garth Gilmour 2008 print "This is verson $] of Perl"; print "Running on the $^O operating system"; print "The current script is $0 "; @myarray = ("ab","cd","ef","gh"); print "Elements are:"; foreach(@myarray) { print " $_ "; } This is verson 5.008008 of Perl Running on the MSWin32 operating system The current script is C:erlpecialScalars.pl Elements are: ab cd ef gh
- 31. © Garth Gilmour 2008 open(INPUT,"MuchAdoAboutNothing.txt"); $count = 1; foreach(<INPUT>) { print("$count: $_"); $count++; } 1: Much Ado About Nothing 2: A comedy by William Shakespear 3: 4: Act 1, Scene 1 5: Before LEONATO'S house. 6: Enter LEONATO, HERO, and BEATRICE, with a Messenger 7: 8: LEONATO 9: I learn in this letter that Don Peter of Arragon 10: comes this night to Messina.
- 33. © Garth Gilmour 2008 print "Enter a number"; $number = <STDIN>; chomp($number); if($number < 10) { print "$number is less than 10"; } elsif($number < 20) { print "$number is less than 20"; } elsif($number < 30) { print "$number is less than 30"; } else { print "$number is greater than 30"; } unless($number % 2 == 0) { print "$number is odd"; } Enter a number 17 17 is less than 20 17 is odd
- 35. © Garth Gilmour 2008 print "Enter a positive number"; $max = <STDIN>; chomp($max); if($max <= 0) { die("Number must be positive!"); } print "Demo of while loop"; print "Numbers from 0 to $max are:"; $count = 0; while($count <= $max) { print "$count"; $count++; } print "Demo of do..while loop"; print "Numbers from 0 to $max are:"; $count = 0; do { print "$count"; $count++; } while($count <= $max); print "Demo of until loop"; print "Numbers from 0 to $max are:"; $count = 0; until($count > $max) { print "$count"; $count++; } print "Demo of do..until loop"; print "Numbers from 0 to $max are:"; $count = 0; do { print "$count"; $count++; }until($count > $max); print "Demo of for loop v1"; print "Numbers from 0 to $max are:"; for($count=0; $count<= $max; $count++) { print "$count"; } print "Demo of for each loop v3"; print "Numbers from 0 to $max are:"; for(0..$max) { print "$_"; }
- 37. Basic Perl I/O Using the Console and Files © Garth Gilmour 2008
- 42. © Garth Gilmour 2008 open(INPUT,"input.txt"); open(OUTPUT,">output.txt"); $count = 0; while($line = <INPUT>) { print OUTPUT ++$count, "", $line; } print "Processed $count lines" This short interval was sufficient to determine d'Artagnan on the part he was to take. It was one of those events which decide the life of a man; it was a choice between the king and the cardinal--the choice made, it must be persisted in. To fight, that was to disobey the law, that was to risk his head, that was to make at one blow an enemy of a minister more powerful than the king himself. All this young man perceived, and yet, to his praise we speak it, he did not hesitate a second. Turning towards Athos and his friends, "Gentlemen," said he, "allow me to correct your words, if you please. You said you were but three, but it appears to me we are four." 1 This short interval was sufficient to determine d'Artagnan on the 2 part he was to take. It was one of those events which decide the 3 life of a man; it was a choice between the king and the 4 cardinal--the choice made, it must be persisted in. To fight, 5 that was to disobey the law, that was to risk his head, that was 6 to make at one blow an enemy of a minister more powerful than the 7 king himself. All this young man perceived, and yet, to his 8 praise we speak it, he did not hesitate a second. Turning 9 towards Athos and his friends, "Gentlemen," said he, "allow me to 10 correct your words, if you please. You said you were but three, 11 but it appears to me we are four."
- 43. © Garth Gilmour 2008 open(INPUT, '<', "input.txt"); open(OUTPUT, '>', "output.txt"); $count = 0; while($line = <INPUT>) { print OUTPUT ++$count, "", $line; } print "Processed $count lines" This short interval was sufficient to determine d'Artagnan on the part he was to take. It was one of those events which decide the life of a man; it was a choice between the king and the cardinal--the choice made, it must be persisted in. To fight, that was to disobey the law, that was to risk his head, that was to make at one blow an enemy of a minister more powerful than the king himself. All this young man perceived, and yet, to his praise we speak it, he did not hesitate a second. Turning towards Athos and his friends, "Gentlemen," said he, "allow me to correct your words, if you please. You said you were but three, but it appears to me we are four." 1 This short interval was sufficient to determine d'Artagnan on the 2 part he was to take. It was one of those events which decide the 3 life of a man; it was a choice between the king and the 4 cardinal--the choice made, it must be persisted in. To fight, 5 that was to disobey the law, that was to risk his head, that was 6 to make at one blow an enemy of a minister more powerful than the 7 king himself. All this young man perceived, and yet, to his 8 praise we speak it, he did not hesitate a second. Turning 9 towards Athos and his friends, "Gentlemen," said he, "allow me to 10 correct your words, if you please. You said you were but three, 11 but it appears to me we are four."
- 44. © Garth Gilmour 2008 open($input, '<', "input.txt"); open($output, '>', "output.txt"); $count = 0; while($line = <$input>) { print $output ++$count, "", $line; } print "Processed $count lines" This short interval was sufficient to determine d'Artagnan on the part he was to take. It was one of those events which decide the life of a man; it was a choice between the king and the cardinal--the choice made, it must be persisted in. To fight, that was to disobey the law, that was to risk his head, that was to make at one blow an enemy of a minister more powerful than the king himself. All this young man perceived, and yet, to his praise we speak it, he did not hesitate a second. Turning towards Athos and his friends, "Gentlemen," said he, "allow me to correct your words, if you please. You said you were but three, but it appears to me we are four." 1 This short interval was sufficient to determine d'Artagnan on the 2 part he was to take. It was one of those events which decide the 3 life of a man; it was a choice between the king and the 4 cardinal--the choice made, it must be persisted in. To fight, 5 that was to disobey the law, that was to risk his head, that was 6 to make at one blow an enemy of a minister more powerful than the 7 king himself. All this young man perceived, and yet, to his 8 praise we speak it, he did not hesitate a second. Turning 9 towards Athos and his friends, "Gentlemen," said he, "allow me to 10 correct your words, if you please. You said you were but three, 11 but it appears to me we are four."
- 46. © Garth Gilmour 2008 open($input, '<', "input.txt") or die "Can't open input"; open($output, '>', "output.txt") or die "Can't open output"; $count = 0; while($line = <$input>) { print($output ++$count, "", $line) or die "Can't write to file"; } print "Processed $count lines"; close($input) or die "Can't close input"; close($output) or die "Can't close output";
- 48. © Garth Gilmour 2008 @exampleDirectories = glob('..'); print "Perl example files are: "; foreach $dir (@exampleDirectories) { @perlFiles = glob($dir . '.pl'); foreach(@perlFiles) { #characters preceding a slash preceding # letters ending in '.pl' m/.*(+pl)/; print "$1 in $dir "; } } Perl example files are: arrayFunctions.pl in ..rrays arraysAndLists.pl in ..rrays days.pl in ..rrays forEach.pl in ..rrays fork.pl in ..oncurrency threads.pl in ..oncurrency customerDB.pl in ..atabases arraysOfArrays.pl in ..ataStructures checkingErrors.pl in ..iles indirectHandles.pl in ..iles basicHashes.pl in ..ashes extraSyntax.pl in ..ashes
- 49. Arrays in Perl Creating and Using Lists © Garth Gilmour 2008
- 51. © Garth Gilmour 2008 $myarray[8] = "string in 9th box"; $myarray[10] = "string in 11th box"; $count = 0; foreach(@myarray) { print $count++,": $_"; } 0: 1: 2: 3: 4: 5: 6: 7: 8: string in 9th box 9: 10: string in 11th box
- 54. © Garth Gilmour 2008 @tstArray = qw(abc def ghi jkl mno pqr); ($first) = @tstArray; ($a,$b,$c) = @tstArray; print "First element is: $first"; print "First three elements are: $a $b $c" First element is: abc First three elements are: abc def ghi
- 57. © Garth Gilmour 2008 @workDays = ("Monday","Tuesday","Wednesday","Thursday","Friday"); @weekendDays = qw(Saturday Sunday); @days = (@workDays,@weekendDays); $numDays = @days; $firstDay = $days[0]; $lastDay = $days[$#days]; print "There are $numDays days in a week"; print "$firstDay is the first day and $lastDay is the last day "; print "The other days are:"; foreach $day (@days) { unless($day eq $firstDay or $day eq $lastDay) { print $day, ""; } } print "The last four days are:"; @lastDays = @days[3..6]; foreach $day (@lastDays) { print $day, ""; }
- 60. © Garth Gilmour 2008 @myarray1 = qw(abc def ghi); $val1 = pop(@myarray1); print "Just popped $val1, contents now:"; foreach(@myarray1) { print "$_"; } push(@myarray1,"zzz"); print "Just pushed zzz, contents now:"; foreach(@myarray1) { print "$_"; } $val1 = shift(@myarray1); print "Just shifted $val1, contents now:"; foreach(@myarray1) { print "$_"; } unshift(@myarray1,"AAA"); print "Just unshifted AAA, contents now:"; foreach(@myarray1) { print "$_"; } Just popped ghi, contents now: abc def Just pushed zzz, contents now: abc def zzz Just shifted abc, contents now: def zzz Just unshifted AAA, contents now: AAA def zzz
- 61. Hashes in Perl Creating and Using Tables © Garth Gilmour 2008
- 63. © Garth Gilmour 2008 $myhash{'k1'} = "abc"; $myhash{'k2'} = 123; $myhash{'k3'} = "def"; $myhash{'k4'} = 456; foreach $key (keys %myhash) { print $key, " indexes ", $myhash{$key}, ""; } k2 indexes 123 k1 indexes abc k3 indexes def k4 indexes 456
- 67. © Garth Gilmour 2008 %myhash = ( k1 => 123, k2 => "abc", k3 => 456, k4 => "def", k5 => 789 ); print "Keys are:"; foreach $key (keys %myhash) { print "", $key, ""; } print "Values are:"; foreach $value (values %myhash) { print "", $value, ""; } print "Entries are:"; while (($key, $value) = each(%myhash)) { print "$key indexes $value "; } Keys are: k5 k2 k1 k3 k4 Values are: 789 abc 123 456 def Entries are: k5 indexes 789 k2 indexes abc k1 indexes 123 k3 indexes 456 k4 indexes def
- 69. © Garth Gilmour 2008 %tstHash = ("k1","v1","k2","v2"); print "Original hash contents:"; foreach(keys(%tstHash)) { print("$_ indexes ",$tstHash{$_},""); } @tstHash {"k3","k4","k5","k6"} = (111,222,333,444); print "Hash contents after insertions:"; foreach(keys(%tstHash)) { print("$_ indexes ",$tstHash{$_},""); } ($var1,$var2,$var3) = @tstHash {"k1","k2","k3"}; print "Values in scalars are $var1 $var2 and $var3"; @elements = %tstHash; print "Array contents:"; foreach(@elements) { print "$_ "; } Original hash contents: k2 indexes v2 k1 indexes v1 Hash contents after insertions: k5 indexes 333 k2 indexes v2 k1 indexes v1 k6 indexes 444 k3 indexes 111 k4 indexes 222 Values in scalars are v1 v2 and 111 Array contents: k5 333 k2 v2 k1 v1 k6 444 k3 111 k4 222
- 71. © Garth Gilmour 2008 %results = ( dave => [54, 62, 73, 48], jane => [59, 67, 82, 70], fred => [92, 64, 59, 71] ); results dave jane fred 54 62 73 48 59 67 82 70 92 64 59 71
- 73. © Garth Gilmour 2008 %actors = ( "george clooney" => ["Oceans 11", "The Peacemaker", "O Brother Where Art Thou"], "harrison ford" => ["Star Wars","Sabrina","Indiana Jones"], "robin williams" => ["Good Morning Vietnam","Hook","The Birdcage"] ); print "The list of actors and their movies is: "; foreach $actor (keys %actors) { print "$actor starred in: "; foreach $film(@{$actors{$actor}}) { print "$film"; } } The list of actors and their movies is: robin williams starred in: Good Morning Vietnam Hook The Birdcage harrison ford starred in: Star Wars Sabrina Indiana Jones george clooney starred in: Oceans 11 The Peacemaker O Brother Where Art Thou
- 74. Regular Expressions Part 1: Core Concepts © Garth Gilmour 2008
- 84. © Garth Gilmour 2008 ABCdefGHIjklMNOpqrSTU [A-Z]{2} Matches: AB GH MN ST ABCdefGHIjklMNOpqrSTU [A-Z]{3} Matches: ABC GHI MNO STU ABCdefGHIjklMNOpqrSTU [A-Z]{3}[a-z] Matches: ABCd GHIj MNOp
- 85. © Garth Gilmour 2008 ABCdefGHIjklMNOpqrSTU [A-Z]+[a-z]+ Matches: ABCdef GHIjkl MNOpqr ABCdefGHIjklMNOpqrSTU ([A-Z]+)([a-z]+) Matches: ABCdef Group 1: ABC Group 2: def GHIjkl Group 1: GHI Group 2: jkl MNOpqr Group 1: MNO Group 2: pqr ABCdefGHIjklMNOpqrSTU [A-Za-z]+ Matches: ABCdefGHIjklMNOpqrSTU
- 86. © Garth Gilmour 2008 ABCdefGHIjklMNOpqrSTU [A-Za-z]{5} Matches: ABCde fGHIj klMNO pqrST ABCdefGHIjklMNOpqrSTU ^[A-Za-z]{5} Matches: ABCde ABCdefGHIjklMNOpqrSTU [A-Za-z]{5}$ Matches: qrSTU ABCdefGHIjklMNOpqrSTU [A-Za-z]{5,8} Matches: ABCdefGH IjklMNOp rqSTU
- 88. Regular Expressions Part 2: Perl Syntax © Garth Gilmour 2008
- 90. © Garth Gilmour 2008 $data = "ABCdefGHIjklMNOpqrSTUvwxYZA"; $m1 = $data =~ m/[A-Z]/; if($m1) { print "Match one is $&"; } $m2 = $data =~ m/[A-Z]{2}/; if($m2) { print "Match two is $&"; } $m3 = $data =~ m/[A-Z]+/; if($m3) { print "Match three is $&"; } $m4 = $data =~ m/[^e]+/; if($m4) { print "Match four is $&"; } $m5 = $data =~ m/[A-Z]{3}[a-z]{2}/; if($m5) { print "Match five is $&"; } Match one is A Match two is AB Match three is ABC Match four is ABCd Match five is ABCde
- 91. © Garth Gilmour 2008 $m6 = $data =~ m/[A-Z]+[a-z]+/; if($m6) { print "Match six is $&"; } $m7 = $data =~ m/[A-Za-z]{9}/; if($m7) { print "Match seven is $&"; } $m8 = $data =~ m/.+/; if($m8) { print "Match eight is $&"; } $m9 = $data =~ m/^.{8}/; if($m9) { print "Match nine is $&"; } $m10 = $data =~ m/.{8}$/; if($m10) { print "Match ten is $&"; } Match six is ABCdef Match seven is ABCdefGHI Match eight is ABCdefGHIjklMNOpqrSTUvwxYZA Match nine is ABCdefGH Match ten is TUvwxYZA
- 92. © Garth Gilmour 2008 @groupOne = $data =~ m/[A-Z]{3}/g; print "First group of matches are:"; foreach(@groupOne) { print "$_"; } @groupTwo = $data =~ m/[a-z]{3}/g; print "Second group of matches are:"; foreach(@groupTwo) { print "$_"; } @groupThree = $data =~ m/.{4}/g; print "Third group of matches are:"; foreach(@groupThree) { print "$_"; } First group of matches are: ABC GHI MNO STU YZA Second group of matches are: def jkl pqr vwx Third group of matches are: ABCd efGH Ijkl MNOp qrST Uvwx
- 95. Using Regular Expressions in Perl © Garth Gilmour 2008 print "Enter the email address:"; chomp($email = <STDIN>); #easier to read version of ([a-z]+([a-z]+)?)megacorp(com|ie|couk) $m = $email =~ m{^ #start of string ( #start of inner match 1 [a-z]+ #one or more lowercase letters ([a-z]+)? #optionally a dot and letters (inner match 2) ) #end of inner match 1 megacorp #company name NB need to escape array (com|ie|couk) #possible domain names $ #end of string }x; if($m) { print "Recognized email for $1 in domain $3"; } else { print "Invalid address!"; }
- 97. © Garth Gilmour 2008 $test = "aabbccddyzeeffgghhiijjkkllmmnnoo"; # Replace all occurances of ff with FF $test =~ s/ff/FF/g; print $test , ""; # Replace any occurance of four characters at the start of the string with XX $test =~ s/^.{4}/XX/g; print $test , ""; # Replace any lower case characters with their upper case equivalents $test =~ s/([a-z])/uc($1)/eg; print $test , ""; aabbccddyzeeFFgghhiijjkkllmmnnoo XXccddyzeeFFgghhiijjkkllmmnnoo XXCCDDYZEEFFGGHHIIJJKKLLMMNNOO
- 98. Regular Expressions Part 3: Advanced Concepts © Garth Gilmour 2008
- 101. © Garth Gilmour 2008 abcDEfghIJklm [a-zA-Z]+[A-Z]{2} abcDEfghIJ Matches: abcDE fghIJ [a-zA-Z]+?[A-Z]{2} [a-zA-Z]*[A-Z]{2} abcDEfghIJklm Matches: ab cDEfg hIJkl [a-zA-Z]*?[A-Z]{2}
- 108. Sample Unicode Properties © Garth Gilmour 2008 Unicode Property Description AHex True for ASCII characters used in hexadecimal numbers Alpha True if a character can be compared to others ea The East Asian width of a character (full, half or narrow) IDC Indicates if a character can only be used as the first in an identifier Math True if the character is used in describing mathematical expressions Lower Indicates if a character is a lowercase letter STerm Indicates if a character is used to terminate a sentence Term Indicates if a character is punctuation that terminates a unit WSpace Indicates if a character should be treated as whitespace during parsing
- 110. Perl Subroutines Creating and Calling Functions © Garth Gilmour 2008
- 112. © Garth Gilmour 2008 sub func { my($param1, $param2, $param3, $param4, $param5) = @_; print "func called with:"; print "$param1"; print "$param2"; print "$param3"; print "$param4"; print "$param5"; } func("abc",123,"def",456,"ghi"); func called with: abc 123 def 456 ghi
- 115. © Garth Gilmour 2008 $var1 = "ABC"; $var2 = "DEF"; $var3 = "GHI"; print "At start $var1, $var2 and $var3"; func1(); print "At end $var1, $var2 and $var3"; sub func1 { my $var1 = "JKL"; local $var2 = "MNO"; our $var3; print "In func1 $var1, $var2 and $var3"; func2(); } sub func2 { print "In func2 $var1, $var2 and $var3"; } At start ABC, DEF and GHI In func1 JKL, MNO and GHI In func2 ABC, MNO and GHI At end ABC, DEF and GHI
- 117. © Garth Gilmour 2008 sub func { my %params = @_; print "Parameter fred has value $params{'fred'}"; print "Parameter wilma has value $params{'wilma'}"; print "Parameter barney has value $params{'barney'}"; } print "---------- First Call ----------"; @args1 = ("fred",20,"wilma",30,"barney",40); func(@args1); print "---------- Second Call ----------"; @args2 = (fred => 50, wilma => 60, barney => 70); func(@args2); print "---------- Third Call ----------"; func(fred => 80, wilma => 90, barney => 100); ---------- First Call ---------- Parameter fred has value 20 Parameter wilma has value 30 Parameter barney has value 40 ---------- Second Call ---------- Parameter fred has value 50 Parameter wilma has value 60 Parameter barney has value 70 ---------- Third Call ---------- Parameter fred has value 80 Parameter wilma has value 90 Parameter barney has value 100
- 119. Subroutines and Recursion © Garth Gilmour 2008 sub recursion1 { until($_[0] == 0) { print "$_[0] "; $_[0]--; &recursion1; } } sub recursion2 { if(@_) { print(shift, " "); &recursion2; } } $val1 = 10; recursion1($val1); print ""; @val2 = qw(abc def ghi jkl); recursion2(@val2); 10 9 8 7 6 5 4 3 2 1 abc def ghi jkl
- 121. © Garth Gilmour 2008 Closures are cool! Closures are cool! Closures are cool! Closures are cool! Closures are cool! Closures are very cool! Closures are very cool! Closures are very cool! ab cd ef gh sub doTimes { for(1..$_[0]) { &{$_[1]}(); } } sub withMatches { for($_[0] =~ m/$_[1]/g) { &{$_[2]}($_); } } $ref = sub { print "Closures are cool!"; }; doTimes(5, $ref); doTimes(3, sub { print "Closures are very cool!"; }); withMatches("ab cd ef gh", "[a-z]{2}", sub { print "$_[0]"; });
- 122. Error Handling Managing Error Conditions © Garth Gilmour 2008
- 124. © Garth Gilmour 2008 eval { op1(); }; if($@) { print "Code threw error: ", $@; } sub op1 { op2(); } sub op2 { op3(); } sub op3 { die "BOOM!"; } eval { op1(); }; if($@) { print "Error of severity ", $@->{'severity'}; print " thrown with message ", $@->{'msg'}; } sub op1 { op2(); } sub op2 { op3(); } sub op3 { my %error = (msg => 'BOOM!', severity => 'fatal'); die error; }
- 125. References in Perl Using Memory Addresses © Garth Gilmour 2008
- 127. © Garth Gilmour 2008 $var1 = 124; $ref1 = var1; print $ref1, ""; print "Reference ref1 refers to value $$ref1"; print "Reference ref1 refers to value ${$ref1}"; SCALAR(0x226d98) Reference ref1 refers to value 124 Reference ref1 refers to value 124
- 128. © Garth Gilmour 2008 @var2 = ("abc","def","ghi","jkl"); $ref2 = var2; print $ref2, “”; print "Reference ref2 refers to array with contents: "; foreach $val (@$ref2) { print "$val "; } print "Reference ref2 refers to array with contents: "; foreach $val (@{$ref2}) { print "$val "; } print "First three elements in array pointed to by ref2 are: "; @slice = @{$ref2}[0..2]; foreach $val (@slice) { print "$val "; } print "First item is $$ref2[0]"; print "First item is ${$ref2}[0]"; print "First item is $ref2->[0]";
- 129. © Garth Gilmour 2008 ARRAY(0x226da4) Reference ref2 refers to array with contents: abc def ghi jkl Reference ref2 refers to array with contents: abc def ghi jkl First three elements in array pointed to by ref2 are: abc def ghi First item is abc First item is abc First item is abc
- 130. © Garth Gilmour 2008 %var3 = ("k1","xxx","k2","yyy","k3","zzz"); $ref3 = var3; print "Reference ref3 refers to hash with contents:"; foreach $key (keys %$ref3) { print "$key indexes $$ref3{$key}"; } print "Reference ref3 refers to hash with contents:"; foreach $key (keys %{$ref3}) { print "$key indexes $ref3->{$key}"; } print "Key k1 indexes $$ref3{'k1'} "; print "Key k1 indexes ${$ref3}{'k1'} "; print "Key k1 indexes $ref3->{'k1'} ";
- 131. © Garth Gilmour 2008 Reference ref3 refers to hash with contents: k2 indexes yyy k1 indexes xxx k3 indexes zzz Reference ref3 refers to hash with contents: k2 indexes yyy k1 indexes xxx k3 indexes zzz Key k1 indexes xxx Key k1 indexes xxx Key k1 indexes xxx
- 133. © Garth Gilmour 2008 $ref1 = ["ab","cd","ef","gh"]; $ref2 = { k1 => 123, k2 => 456, k3 => 789 }; $ref3 = sub { return $_[0] + $_[1]; }; print $ref1, ""; print $ref2, ""; print $ref3, ""; print $ref1->[0], ""; print $ref2->{'k1'}, ""; print $ref3->(12,5), ""; ARRAY(0x225f88) HASH(0x226d80) CODE(0x18303f0) ab 123 17
- 135. © Garth Gilmour 2008 @numerals = ( [100,"C"], [90,"XC"], [50,"L"], [40,"XL"], [10,"X"], [9,"IX"], [5,"V"], [4,"IV"], [1,"I"] ); print "Enter the number to convert to a roman numeral..."; $number = <STDIN>; chomp($number); foreach (@numerals) { my $decimal = $_->[0]; my $string = $_->[1]; my $times = int($number / $decimal); if($times > 0) { for(1..$times) { print $string; } $number = $number % $decimal; } }
- 136. © Garth Gilmour 2008 $ref1 = [ ["abc","def","ghi"], ["jkl","mno","pqr"], ["stu","vwx","yza"] ]; print "Contents of 2d array are:"; foreach(@{$ref1}) { print ""; foreach(@{$_}) { print "$_ "; } print ""; } Contents of 2d array are: abc def ghi jkl mno pqr stu vwx yza
- 137. © Garth Gilmour 2008 $ref = { k1 => { k4 => "ab", k5 => "cd" }, k2 => { k6 => "ef", k7 => "gh" }, k3 => { k8 => "ij", k9 => "kl" } }; print $ref->{'k1'}->{'k4'}, ""; print $ref->{'k1'}->{'k5'}, ""; print $ref->{'k2'}->{'k6'}, ""; print $ref->{'k2'}->{'k7'}, ""; print $ref->{'k3'}->{'k8'}, ""; print $ref->{'k3'}->{'k9'}, ""; ab cd ef gh ij kl
- 138. Modules and Packages Creating Reusable Code © Garth Gilmour 2008
- 142. © Garth Gilmour 2008 package Maths; require Exporter; our @ISA = ("Exporter"); @EXPORT = qw(add multiply subtract); sub add { return $_[0] + $_[1]; } sub divide { return $_[0] / $_[1]; } sub multiply { return $_[0] * $_[1]; } sub subtract { return $_[0] - $_[1]; } use Maths; print "Calculations using our maths module:"; print "40 + 30 is: ", add(40,30); print "60 - 20 is: ", subtract(60,20); print "50 * 10 is: ", multiply(50,10); # divide is not exported so it only works # if we qualify the namespace print "40 / 10 is: ", Maths::divide(40,10);
- 143. © Garth Gilmour 2008 package Maths; require Exporter; our @ISA = ("Exporter"); @EXPORT_OK = qw(add multiply subtract); sub add { return $_[0] + $_[1]; } sub divide { return $_[0] / $_[1]; } sub multiply { return $_[0] * $_[1]; } sub subtract { return $_[0] - $_[1]; } use Maths qw(add multiply subtract); print "Calculations using our maths module:"; print "40 + 30 is: ", add(40,30); print "60 - 20 is: ", subtract(60,20); print "50 * 10 is: ", multiply(50,10); # divide is not exported so it only works # if we qualify the namespace print "40 / 10 is: ", Maths::divide(40,10);
- 145. Objects in Perl Support for Object Oriented Programming Concepts © Garth Gilmour 2008
- 148. © Garth Gilmour 2008 Client Code Account Objects account1 account2 withdraw { … } display { … } withdraw { … } display { … }
- 149. © Garth Gilmour 2008 class Account: def __init__(self,id,balance): self.id = id self.balance = balance def withdraw(self, amount): self.balance -= amount def display(self): print "Account with id", self.id, "and balance", self.balance account1 = Account("AB12",30000) account2 = Account("CD34",45000) print "----- Before Withdrawl -----" account1.display() account2.display() account1.withdraw(250) account2.withdraw(500) print "----- After Withdrawl -----" account1.display() account2.display() ----- Before Withdrawl ----- Account with id AB12 and balance 30000 Account with id CD34 and balance 45000 ----- After Withdrawl ----- Account with id AB12 and balance 29750 Account with id CD34 and balance 44500 Constructor Class Declaration Creating Objects
- 150. © Garth Gilmour 2008 class Account def initialize(id, balance) @id = id @balance = balance end def withdraw(amount) @balance -= amount end def display() puts "Account with id #{@id} and balance #{@balance}" end end account1 = Account.new("AB12",30000) account2 = Account.new("CD34",45000) puts "----- Before Withdrawl -----" account1.display() account2.display() account1.withdraw(250) account2.withdraw(500) puts "----- After Withdrawl -----" account1.display() account2.display() ----- Before Withdrawl ----- Account with id AB12 and balance 30000 Account with id CD34 and balance 45000 ----- After Withdrawl ----- Account with id AB12 and balance 29750 Account with id CD34 and balance 44500 Class Declaration Constructor Creating Objects
- 152. © Garth Gilmour 2008 package Account; sub new { my $packageName = shift; my $data = {}; $data->{'id'} = shift; $data->{'balance'} = shift; bless $data, $packageName; } sub withdraw { my $data = shift; $data->{'balance'} -= $_[0]; } sub display { my $data = shift; print "Account with id $data->{'id'} and balance $data->{'balance'}"; } Packages double as classes Any method can be a constructor Anonymous hashes hold fields
- 153. © Garth Gilmour 2008 $account1 = Account->new("AB12",30000); $account2 = Account->new("CD34",45000); print "----- Before Withdrawl -----"; $account1->display(); $account2->display(); $account1->withdraw(250); $account2->withdraw(500); print "----- After Withdrawl -----"; $account1->display(); $account2->display(); ----- Before Withdrawl ----- Account with id AB12 and balance 30000 Account with id CD34 and balance