Ruby - Condition (if), Operators (comparison/logical) & case statement 2020

Let's learn how to use conditional statement in Ruby:

#!/usr/bin/ruby
# r9.rb
# if - elsif - else - end

age = 12

if (age <= 2)
  puts "You're a baby"
elsif (age > 2 ) && (age < 12 )
  puts "You're a kid"
else
  puts "You're almost there"
end

Output:

$ ./r9.rb
You're almost there

Here are the common operators in Ruby.

==, !=, > , <, =>, <=

Other comparison operators are:

Another comparison operator, unless. It is just if in reverse. It's a conditional statement that executes only if the condition is false:

#!/usr/bin/ruby
# r10.rb
# comparison operators : unless

age = 12
unless age > 5
   puts "No school"
else
   puts "Go to school"
end

Output:

$ ./r10.rb
Go to school

#!/usr/bin/ruby
# r11.rb
# logical operators

puts "true && false = " + (true && false).to_s
puts "true || false = " + (true || false).to_s
puts "!true = " + (!true).to_s

Output:

$ ./r11.rb
true && false = false
true || false = true
!true = false

#!/usr/bin/ruby
# r12.rb
# case statement

number = gets.chomp  # remove a new line
case number
when "one", "uno"
   puts "1"
   exit
when "two", "dos"
   puts "2"
   exit
else
   puts "too big"
end

Output:

$ ./r12.rb
dos
2
k@laptop:~/TEST/RUBY$ ./r12.rb
10
too big

#!/usr/bin/ruby
# r13.rb
# ternary condition

age = 86

puts (age >= 70? "old" : "still young")

Output:

$ ./r13.rb
old