13r.1 revision (q&a). 13r.2 $scalar = @arr; 13r.3 multiple assignment my ($a,$b,@c,@d,@e);...

13r.1

Revision (Q&A)

13r.2

$scalar = @arr;

13r.3 Multiple assignment

my ($a,$b,@c,@d,@e);

$(a,$b'( = )cow','dog;)'

$(a,$b,@c( = )1,2,3,4,5;)

@e = (6,7,8,9,10);

$(a,$b@ = )e;

$a = @e;

$(a@ = )e;

@d = ($a, $b);

@e = (@c,@d);

Multiple declarations

$a='cow' $b='dog'

$a=1; $b=2; @c=(3,4,5)

@e=(6,7,8,9,10);

$a=6; $b=7

$a=5;

$a=6;

@d=(6,7)

@e=(3,4,5,6,7);

will be useful for home assignment

13r.4

use strict;

my ($inFile,$outFile) = ('D:\fight club.txt','D:\sorted.txt');

open(IN, "<$inFile") or die "cannot open $inFile";

open(OUT, ">$outFile") or die "cannot open $outFile file";

my @lines = <IN>;

my @sorted = sort(@lines);

print OUT @sorted;

close(IN);

close(OUT);

Working with files - example

© 1999 - 20th Century Fox - All Rights Reserved

13r.5

use strict;

my ($inFile,$outFile) = @ARGV;

open(IN, "<$inFile") or die "cannot open $inFile";

open(OUT, ">$outFile") or die "cannot open $outFile file";

my @lines = <IN>;

my @sorted = sort(@lines);

print OUT @sorted;

close(IN);

close(OUT);

Working with files - example

© 1999 - 20th Century Fox - All Rights Reserved

D:\> perl -w sortFil.pl "D:\fight club.txt" "D:\sorted.txt"

13r.6

Subroutines

13r.7

A function is a portion of code that performs a specific task.

Functions

Functions can have arguments and return values:

$start = substr ($str,1,4);

Arguments:(STRING, OFFSET,

LENGTH)

Return value:This function returns a string

13r.8

my $bart4today = "I do not have diplomatic immunity ;"

bartFunc($bart4today ,100);

sub bartFunc {

my ($string, $times) = @_;

print $string x $times;

}

Subroutine example

I do not have diplomatic immunity




...

13r.9

$reversed = reverseComplement("ACGTTA");

A subroutine may be given arguments through the special array variable _@

Return value

sub reverseComplement {

my ($seq) = @_;

$seq =~ tr/ACGT/TGCA/;

my $revSeq = reverse $seq;

return $revSeq;

}

When a subroutine is invoked, perl begins to run it

separately from the main program

$reversed

13r.10

$reversed = reverseComplement( );

Passing arguments :

Return value


my ($seq) = @_;



return $revSeq;

}Arguments are passed using the special array

_@

_@

"ACGTTA""ACGTTA"

$reversed

13r.11


Passing arguments :

Return value


($seq) = @_;



return $revSeq;

}We can then read the

arguments from _@

"ACGTTA"$reversed

_@

"ACGTTA"

$seq "ACGTTA"

13r.12

$seq "ACGTTA"


Return value


my ($seq) = @_;



return $revSeq

} We can now add whatever content we want to the

subroutine

"ACGTTA"

_@

"ACGTTA"

$reversed

$seq "TGCAAT"

$revSeq "TAACGT"

13r.13


Returning return values :

Return value


my ($seq) = @_;



return $revSeq;

}

"ACGTTA"

The return statement ends the execution of the

subroutine and returns a value

$reversed

_@

"ACGTTA"

$seq "ACGTTA"$seq "TGCAAT"

$revSeq "TAACGT" "TAACGT"

13r.14

my @petArr = ('Liko','Emma','Louis');

printPets (\@petArr);

Passing references:

Passing variables by reference

sub printPets {my ($petRef) = @_;foreach my $pet (@{$petRef}) { print "Good $pet\n";}

}

@petArr

We create a reference to the array

'Emma''Liko' 'Louis'

13r.15



Passing references:



}

_@

@petArr

Then we pass the reference to the

subroutine

13r.16



Passing references:



}

_@

$petRef

@petArr

13r.17



Passing references:



}

_@

$petRef

@petArr

Good LikoGood EmmaGood Louis

13r.18

Referencing, De-referencing

13r.19

%bookHash%bookHash

ReferencesYou can think of it as folders that contain inner folders that contains some data…

$bookHash{"Eyal"}->{"phone"} = 5012;

$bookHash{"Eyal"}->{"address"} = "Swiss;"

$bookHash{"Neta"}->{"phone"} = 6023;

$bookHash{"Neta"}->{"address"} = "Yavne;" 5012"phone"

"Swiss""addrs"

"Eyal"

6023"phone"

"Yavne""addrs"

"Neta"

$bookHash{"Eyal"}{"phone"} = 5012 ;

$bookHash{"Eyal"}{"address"} = "Swiss;"

$bookHash{"Neta"}{"phone"} = 6023 ;

$bookHash{"Neta"}{"address"} = "Yavne;"

Change Neta's address:

$bookHash{"Neta"}{"address"} = "Tel-Aviv;"

Change Eyal's phone:

$bookHash{"Eyal"}{"phone"} = 2209;

13r.20

The general structure of the data structure:

$ #bookHash{$name}{"address"} = $address

$ #bookHash{$name}{"phone"} = $phone

Get all the phones:

@names= keys(%bookHash)

foreach my $name (@names)}

print "Phone of $name;" :

print $bookHash{$name}{"phone"}."\n;"

{

De-referencing examples

13r.21

Get all the details of Neta:

my %NetaDetails= %{$bookHash{"Neta"}}

Get the phone of Eyal:

my $EyalPhone = $bookHash{"Eyal"}->{"Phone"};

De-referencing examples

%bookHash%bookHash

5012"Phone"

"Swiss""Addrs"

"Eyal"

6023"Phone"

"Yavne""Addrs"

"Neta"

13r.22

Referencing array:

$arrayRef = [@grades];

$gradesRef = \@grades; (careful)

Referencing – Dereferencing ArraysDereferencing array:

@arr = @{$arrRef};

$element1 = $arrRef->[0];

B CA

@grades$gradesRef

B CA

$arrRef

B CA

@arr

$element1 = $arrRef->[0] = A

13r.23

Referencing hash:

$hashRef = {%phoneBook};

$bookRef = \%phoneBook; (careful)

Referencing – Dereferencing Hashes - summary

Dereferencing hash:

%hash = %{$hashRef};

$myVal = $hashRef->{"A"};

$bookRef %phoneBook

XA

YB

ZC

$hashRef

XA

YB

ZC

%hash

XA

YB

ZC

$myVal = $hashRef->{"A"} = "X"

13r.24

While & Foreach

13r.25Loops: while (defined …)

Let's observe the following code :open (IN, "<numbers.txt");my $line = <IN>;while (defined $line) {

chomp $line;if ($line > 10) {

print $line;}$line = <IN>;

}close (IN);

13r.26Foreach loops

open (IN, "<numbers.txt");

my @lines = <IN;<

chomp @lines;

foreach my $num (@lines)} if ($num <= 10) }next ;

{print $num ;

{

close (IN);

13r.1 revision (q&a). 13r.2 $scalar = @arr; 13r.3 multiple assignment my ($a,$b,@c,@d,@e);...

Documents