Learning ruby - day 1

print "Hello World!!!"

PS D:\Workplace> ruby hello-world.rb
Hello World!!!

print "First line "
print "still first line\n"
puts "Second line"
puts "Thirld line"

First line still first line
Second line
Thirld line

print else

main

num = 2
print num.even?

true

num = 2
num.div 2
print num

1

array = [1, 2, 3, 4, 5]
array.each do |num|
    puts num.pow 2
end

1
4
9
16
25

def print_char(array)
    array.each do |num|
        puts num.chr unless num.odd?
    end
end
array = [65, 66, 67, 68, 69, 70, 71]
print_char(array)

B
D
F

arr.pop

arr.shift

arr.delete_at(2)

arr.delete(5)

arr.delete_if {|a| a < 2}

arr.keep_if {|a| a < 4}

arr2 = arr.select {|a| a > 2}
print arr2

arr2 = arr.reject {|a| a > 2}

arr2 = arr.drop_while {|a| a > 1}

# initialize and set default value
empty_hash = Hash.new 
empty_hash.default = 1
# or
default_hash = Hash.new(1)

new_hash = {"key1" => 12, "key2" => 50}
# or
new_hash = Hash.new
new_hash["key1"] = 12
new_hash["key2"] = 50
# or
new_hash.store("key1", 12)
new_hash.store(1512032, 50)

hash.each do |key, value|
    puts key
    puts value
end
# or
hash.each do |array|
    # now key is array[0], value is array[1]
    puts array[0]
    puts array[1]
end

# Delete specific key
hash.delete("key1")
# Delete if
hash.keep_if {|key, value| key.is_a? Integer} 
# or 
hash.delete_if {|key, value|key.even? }

i = 0
loop do
    puts i
    i += 1
    break if i == 10
end

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10