conditions

# Conditions: `if`, `elsif`, `else`, `unless`, and `if` as a value.

temperature = 23

if temperature > 30
  puts "hot"
elsif temperature > 20
  puts "warm"
else
  puts "cold"
end

# `unless` is `if not`.
unless temperature < 0
  puts "above freezing"
end

# A one-line form goes after the statement.
puts "nice day" if temperature == 23

# `if` is an expression, so it can be assigned.
label = if temperature > 20
          "warm"
        else
          "cool"
        end
puts label

# The short form: condition ? when true : when false.
puts temperature.even? ? "even" : "odd"

# `&&`, `||`, `!` combine conditions.
puts temperature > 20 && temperature < 30
puts !(temperature > 20)