Crystal by example: If/Else

The if and else structures are conditional structures; they check whether a value is true or false and execute code based on that. Crystal has if, else, and unless to handle conditions.

The if and unless structures do not depend on else, which means you don’t need to use else every time.

unless is the opposite of if.

elsif is a sub-structure that is optional but is used to handle another if when the first condition is false. There can be many elsif statements in the code.

Crystal also has ternary operators, which are a short version of if else. The language also supports suffix conditions, allowing values to be assigned conditionally.

a = 5

if a > 10
  puts "a is bigger than 10!"
end

unless a > 10
  puts "a is not bigger than 10!"
end

if a >= 6
  puts "a is equal or bigger than 6"
else
  puts "a is not equal or bigger than 6"
end

y = a * 2

if a == y
  puts "a is equal to y"
elsif a >= y
  puts "a is equal or bigger than y"
else
  puts "a have no correlation with y"
end

b = 2 < 3 ? 3 : 4
b = 5 if a < y

puts b

$ crystal run if-else.cr

a is not bigger than 10!
a is not equal or bigger than 6
a have no correlation with y
5
a is not bigger than 10!
a is not equal or bigger than 6
a have no correlation with y
5