Arrays

hash1.rb

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z = { 'mike' => 75, 'bill' => 18, 'alice' => 32 }
z['joe'] = 44
print z['bill'], " ", z['joe'], " ", z["smith"], "\n"
print z.has_key?('mike'), " ", z.has_key?("jones"), "\n"

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Ruby hashes are similar to maps or dictionaries in other languages. They are essentially arrays whose subscripts are not limited to integer values. You can create them with the curly-bracked list notation shown, but you can also assign to a subscript expression to add members. It's not at all unreasonable to create a hash with empty brackets, then add members using subscripting.

Method names may end in ?, hence the name of the has_key? method. This suggests a the method is a test which returns a boolean value. Such methods are sometimes known as predicates.

Arrays

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