up

Perl Lecture Notes - September 14

• Why Perl and Java?
  • "Not too much" vs "not too few" technologies
  • Popularity; available libraries and code
  • Radically different but both C-ish
  • Open Source / Standards
  • Perl strengths and weaknesses
  • Sample Perl code:
    • hello.pl
    • hello_world.pl
    • template
    • one_to_ten_A
    • one_to_ten_B
    • troy_brooks_haiku
    • obfuscated Perl

• Getting started 1 - administration and background
  • 3 trimester basic schedule for IPL
  • Perl Books: what each is for; "Learning" pro's / con's; Camel book.
  • The wiki and other class websites
  • contacting us
  • grading policies and submitting work ( via online gradebook; still coming )

• Getting started 2 - nuts and bolts of writing/running/debugging perl
  • unix and ssh-ing in
  • installing Perl and/or getting access to it: unix, mac, windows
  • manuals, documention, resources
  • editors: emacs, xemacs, vim, ...
  • use "perl -w your_file" to see warnings
  • use "perl -d your_file" to invoke the debugger (more later on this)
  • use "perl -de1" for "interactive" attempts
  • making it executable : #!/bin/perl and chmod +x filename
  • organizing your assignments and work on bob/~you/

• Diving in with Perl data types : $, @, %, & and syntax assumptions
  • syntactic definition with special symbols - like language word endings.
  • Motivation: print " The answer is $foo "
  • Data types:
    • $foo = scalar (string, int, real, reference)
    • @foo = array
    • %foo = hash ( coming )
    • &foo = subroutine (coming )
  • Strings: quotes, interpretation, "here-is", . concatenation
  • Int/Real (and String) auto-conversion, 1, 1.2e-3, others
  • Boolean: "", (), 0, undef : false
  • Array
    • @foo = ( 1, "hello", 4, (2 , "six" ) ); # gives list
    • $foo[1] # is "hello"
    • @foo[0..3] # is (1, "hello", 4, 2)
  • scalar vs array "context".
  • many, many built-in functions: length, reverse, sort, ...
  • function calls may omit () : print("hello") vs print "hello" (so how does it know when to stop? Depends on what it tries to grab...)
  • Some cases that may not do what you expect :
    1. $a = (10, 20, 30);
    2. @a = 3;
    3. @a = (10, 20, 30);
    4. ($a) = (10, 20, 30);
    5. $b = @a; # compare with first example...
    6. $a = 1, 2, 3
    7. print "hi", "there", "you";
    8. print length "hi, "there", "you";
    9. print (2+3)*5, "is the answer";
  • if time allows (or read in Llama): if, while, chomp, STDIN, print, qw, pop, push, shift, sort, reverse, " $interpolation ", #comments, foreach, $_

• Assignment:
  • Read chapters 1, 2, 3 in the Llama book.
  • Install perl on your home machine and/or explore ways to use it on bob.marlboro.edu and your linux box. Try out vi. Try out emacs. Play around.
  • Do Llama 1.1, 2.4, 3.3

• Are we having fun yet?