What are curly braces in the Ruby programming language?

Curly braces {} in Ruby are used in several contexts:

1. Defining code blocks (blocks):

   • For single-line blocks or when the block contains little code.

   # Example of using a block with the `each` method
   [1, 2, 3].each { |n| puts n * 2 }
   
   # Example of using a block with the `map` method
   doubled_numbers = [1, 2, 3].map { |n| n * 2 }
   

2. Defining hashes (Hashes):

   • For creating hash literals.

   # Example of creating a hash with symbols as keys
   user = { name: "Alice", age: 30 }
   
   # Example of creating a hash with different key types
   settings = { "theme" => "dark", :notifications => true, 1 => "value" }
   

3. Nested data structures:

   • Along with square brackets [] for creating nested arrays and hashes.

   # Example of a nested hash in an array
   data = [{ id: 1, value: "A" }, { id: 2, value: "B" }]
   
   # Example of a nested array in a hash
   config = { users: ["Alice", "Bob"], roles: ["admin", "user"] }