til/ruby/triple-equals-the-case-equality-operator.md

Triple Equals: The Case Equality Operator

The standard equality operator in Ruby is the double equals (==).

> 2 + 2 == 4
=> true

Ruby supports another operator that looks sneakily like this, but with different behavior. It's the triple equals (===) which is called the case equality operator (or case subsumption operator).

Though the specific behavior can be overridden on a class by class basis, the operator is generally used to check if the first operand is a bucket that the second operand fits into.

Here are some examples:

> (1..10) === 5
=> true
> (1..10) === 13
=> false

> Integer === 7
=> true
> Integer === 'nope'
=> false

> /fun/ === "fundamentals"
=> true
> /taco/ === "fundamentals"
=> false

> Object === String
=> true
> String === Object
=> false

It's important to understand how this works because === is the operator used under the hood by Ruby's case statements.

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