perl_tutorial, Perl

perl_tutorial

#perl 5.22.1

use strict;
use warnings;

print "Hello World\n";

#scalars store any integr single value

my $g = 12;
my $h = 15;
my $apple_variety = "Red, delicious";

#arrays store any number of ordered scalars

my @first_array = (1,2,3,4,5,6,7,8,9);
my @second_array = ("strings", "also", "work", "and spaces");

$first_array[3] = 99; #change single array item
$first_array[-1] = 12; #- count array in reverse order

my @fast_array = qw(hola hello como estas);
my @numbers = (23, 23, 23, 23, 23);
my @composite = (4,6,8..10,12,14..16);

my @veggies = qw(spinach lettuce oninons);
my @fruits = qw(apple banana pairs);

my @grocery_list = (@fruits, @veggies, "milk");

#unshift operation (append to head of list and prints number of elements, shift right)
print "@grocery_list\n";
print unshift(@grocery_list, "avocado");
print "\n";
print "@grocery_list\n";

#shift operation (removes top element of list and prints element removed, shift left)
print shift(@grocery_list);
print "\n";
print "@grocery_list\n";

#pop operation (pops out last element of the list)
print pop(@grocery_list);
print "\n";
print "@grocery_list\n";

#push operation (pushes in one element to the tail of the list)
print push(@grocery_list, "avocado", "salt");
print "\n";
print "@grocery_list\n";

#slicing arrays
#$array[1] is scalar, @array[1] is array with a single value

my @video_games = qw(smash naruto minecraft cod dota);
my @fav_games = @video_games[0,4];

push(@fav_games, "agario");
unshift(@fav_games, "coolgame");

print "@fav_games\n";

#iterating over arrays
foreach my $x (@fav_games){
    print "this game is $x\n";
}

#hashes: stores scalars as unorganized key values

my %first_hash = (horses => 4, swords => 7, mages => 3);
print "Our army has $first_hash{horses} horses, $first_hash{swords} swords\n";
$first_hash{horses} = 10; #changing hash value
print "Our army has $first_hash{horses} horses, $first_hash{swords} swords\n";

#can be delcared in many different ways
my %deserts1 = (cake => "apple", cheesecake => "strawberry", sorbet => "lime");
my %deserts2 = ("cake", "apple", "cheesecake", "strawberry", "sorbet", "lime");
my %deserts3 = qw(cake apple cheesecake strawberry sorbet lime);

print "$deserts1{cake} cake, with a $deserts2{cheesecake} chck and $deserts3{sorbet} sorbet\n";

#delete with delete keyword
delete $deserts3{sorbet};

#hash slicing, both forms work

my @desert_fruits = ($deserts1{cake}, $deserts1{cheesecake}, $deserts1{sorbet});
my @desert_fruits2 = @deserts2{"cake", "cheesecake", "sorbet"};

print "@desert_fruits\n";
print "@desert_fruits2\n";

#hash iteration, note the syntax!
my @desertsx = keys %deserts1;
my @fruitsx = values %deserts1;

while (my ($desertsx, $fruitsx) = each %deserts1)
{
    print "I have a $fruitsx $desertsx\n";
}

#operators (same as other programming languages
#numeric operators
my $numx = 3;
$numx *= 10;
print "$numx\n";

my $bit1 = 7; #111
my $bit2 = 5; #101

#shift right
$bit1 = $bit1 >> 1; #becomes 011 
$bit2 = $bit2 >> 1; #becomes 010

#shift left 
$bit1 = $bit1 << 1; #becomes 110 
$bit2 = $bit2 << 1; #becomes 100

print "$bit1\n";
print "$bit2\n";

#string operators
my $stringy = "hello there";
$stringy.=" stranger "; #appending string to the end of string
print "$stringy\n";

$stringy x= 3; #repeating
print "$stringy\n";

#boolean values -> not real boolean values in perl
my @books = qw(sapiens ai thinking);

print "They are both books\n" if ($books[0] == $books[1]); #type equality
print "They are both the same book\n" if ($books[0] eq $books[0]); #comparing the string

#useful array operations
#sort, reverse, push/pop, shift/unshift, split/join, grep, map

#sort
my @number_collection = qw(1 9 5 7);
print "@number_collection\n";
@number_collection = reverse(@number_collection); #reversing order of array
print "@number_collection\n";
@number_collection = sort(@number_collection); #sorting in numerical order
print "@number_collection\n";

#reverse
my @words = qw(table chair pencil apple book);
print "@words\n";
@words = reverse(@words); #reversing order of array
print "@words\n";
@words = sort(@words); #sorting strin array in alpahabetical order
print "@words\n";

#join (array -> string)
my @utensils = qw(spoon fork knife);
my $utensil_string = join(" and a ", @utensils); #joins each element with a string
print "$utensil_string\n";

#split (string -> array)
my $sports = "swimming gym frisbee";
my @sports_array = split(" ", $sports);
print "@sports_array\n";

#grep (get elements that contain certain grep)
my @juices = qw(apple oraage pear apple-strawberry bannana-apple lime);
my @apple_juices = grep(/apple/, @juices);
print "This are the juices that contain apple: @apple_juices\n";

#can also be used in numbers
my @numberss = qw(1 2 3 4 5 6 7 8 9 10);
my @thic_numbers = grep{$_>5} @numberss; #both formats are acceptable
my @small_numbers = grep($_<4, @numberss);
print "@thic_numbers\n";
print "@small_numbers\n";

#map
my @multiplied_numbers = map($_*2, @numberss);
print "This are the multiplied numbers: @multiplied_numbers\n";

#maps also works with conditions
my @big_numbers = map($_>10 ? $_ : (), @multiplied_numbers);
print "This are the big numbers: @big_numbers\n";

#flow control
#conditionals -> if, unless
#loops

#test to see this works


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