Barcelona Perl Mongers

Curs de Perl2012-11-10

Dades i Operadors

Dades I Operadors

● tipus bàsics: $scalar @array %hash● cadenes de caràcters● operadors numèrics i de cadenes● control del flux: condicionals, bucles i errors● entrada/sortida: STDIN STDOUT

* Before we start...

$ perldoc

#!/usr/bin/perl#!/usr/bin/env perl

use strict;

Datos y Operadores

Datos Escalares

● Strings● Numbers

Strings

Datos de texto o binarios, sin significado para el programa, delimitados tipicamente por comillas

sencillas o dobles:

Strings

my $world = 'Mundo';my $escaped = 'Dan O\'Bannon';

my $backslash = '\\';

Comillas dobles

my $newline = "\n";my $tab = "\t";my $input = "hello\nworld!";my $data = "08029\t25";my $data = "08029,\"Eixample Esquerra\"";my $data = qq{08029,"Eixample Esquerra"};

Interpolacion

my $hello = "Hola, $world!\n";my $hello = qq{Hola, "$world"!\n};

Funciones tipicas de cadena

length EXPRsubstr EXPR,OFFSET,LENGTH,REPLACEMENTsubstr EXPR,OFFSET,LENGTHsubstr EXPR,OFFSETindex STR,SUBSTR,POSITIONindex STR,SUBSTR

Functions for SCALARs or strings

"chomp", "chop", "chr", "crypt", "hex", "index","lc", "lcfirst","length", "oct", "ord", "pack", "q//",

"qq//","reverse", "rindex","sprintf", "substr", "tr///", "uc", "ucfirst", "y///"

=> Mas cuando hablemos de expresiones regulares

Numeros

perldoc perlnumber:

$n = 1234; # decimal integer

$n = 0b1110011; # binary integer

$n = 01234; # *octal* integer

$n = 0x1234; # hexadecimal integer

$n = 12.34e−56; # exponential notation

$n = "−12.34e56"; # number specified as a string

$n = "1234"; # number specified as a string

Hashes, Listas y Arreglos

@ Arreglo

my @author; $author[0] = 'Asimov';$author[1] = 'Bear';$author[2] = 'King';print "First author is " . $author[0] . "\n";print "Last author is " . $author[$#author] . "\n";print "Last author is " . $author[-1] . "\n";print "There are " . @author . " authors\n";my @num = (0..10);my @a = (@b,@c);

# ++$learn

$ perldoc List::Util

% Hash

my %name; $name{'Asimov'} = 'Isaac'; $name{'Bear'} = 'Greg'; $name{'King'} = 'Stephen';

Funciones tipicas para hashes

keys HASHvalues HASH print "Authors are ".keys(%name)."\n";

Identificadores, variables y su notacion

Notacion

Las variables son precedidas de un sigil que indica el tipo de valor de la variable:

$ Escalar@ Arreglo% Hash

e.g.my($nombre, @nombre, %nombre);

Para acceder el elemento de un arreglo o hash, se utiliza el sigil escalar:

$nombre{$id} = 'Ann';$nombre[$pos] = 'Ben';

Es posible acceder multiples valores al mismo tiempo utilizando el sigil de arreglo:@nombre{@keys} = @values;@suspendidos = @nombre[@selected];@authors =("Asimov","Bear","King");@authors = qw(Asimov Bear King);

Variables especiales

$ perldoc perlvar$ perldoc English @ARGV @INC %ENV %SIG $@@_ $_

I/O

Consola

STDINSTDOUTSTDERR

e.g.

print STDERR "This is a debug message\n";

Operadores y su precedencia

( y su asociatividad ( y su arity ( y su fixity ) ) )

$ perldoc perlop left terms and list operators (leftward) left −> nonassoc ++ −− right **right !~\ and unary + and − left =~ !~ left */%x left +−. left << >> nonassoc named unary operators nonassoc <><=>=ltgtlege nonassoc ==!=<=>eqnecmp~~ left & left |^ left && left || // nonassoc .. ... right ?: right =+= −= *= etc. left ,=> nonassoc list operators (rightward) rightleftleftnot and or xor

=> Atencion!

print ( ($foo & 255) + 1, "\n"); print ++$foo;

* Operadores

* Numericos* String

* Logicos* Bitwise

* Especiales

* Estructuras de Control

if (EXPR) BLOCK if (EXPR) BLOCK else BLOCK

if (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK LABEL while (EXPR) BLOCK

LABEL while (EXPR) BLOCK continue BLOCK LABEL until (EXPR) BLOCK

LABEL until (EXPR) BLOCK continue BLOCK LABEL for (EXPR; EXPR; EXPR) BLOCK

LABEL foreach VAR (LIST) BLOCK LABEL foreach VAR (LIST) BLOCK continue BLOCK

LABEL BLOCK continue BLOCK

e.g.

for(my $i=0; $i<@author; ++$i) { print $i.": ".$author[$i]."\n";}

for(0..$#author) { print $_.": ".$author[$_]."\n";}

foreach my $i (0..$#author) { print $i.": ".$author[$i]."\n";}

for(0..1000000) { print $_,"\n";}

while(<$fh>) { ... }

* Modificadores

if EXPR unless EXPR while EXPR until EXPR

foreach LISTnext if /^#/;

...

e.g.

print "Value is $val\n" if $debug; print $i++ while $i <= 10;

Contexto

* Voidfind_chores();

* Listamy @all_results = find_chores();my ($single_element) = find_chores();process_list_of_results( find_chores() );my ($self,@args) = @_;

* Escalarprint "Hay ".@author." autores\n";print "Hay ".scalar(@author)." autores\n";

# ++$learn

$ perldoc -f wantarray

* Numerico

my $a = "a";my $b = "b";print "a is equal to b " if ($a==$b); # Really?print "a is equal to b " if ($a eq $b);

* Cadena

my $a = 2;print "The number is ".$a."\n";

* Booleano

my $a = 0;print "a is true\n" if $a;$a = 1;print "a is true\n" if $a;$a = "a";print "a is true\n" if $a;my $numeric_x = 0 + $x; # forces numeric contextmy $stringy_x = '' . $x; # forces string contextmy $boolean_x = !!$x; # forces boolean context

string context

my $boolean_x = !!$x; # forces boolean context

string context

my $boolean_x = !!$x; # forces boolean context