This page contains automated test results for code from O'Reilly's Ruby Cookbook. If this code looks interesting or useful, you might want to buy the whole book.

Creating a Hash with a Default Value (written by Ben Giddings)
CodeExpectedActual
h = Hash.new
h[1]
 nil nil 
h['do you have this string?']
 nil nil 
h = Hash.new("nope")
h[1]
 "nope" "nope" 
h['do you have this string?']
 "nope" "nope" 
h = Hash.new { |hash, key| (key.respond_to? :to_str) ? "nope" : nil }
h[1]
 nil nil 
h['do you have this string']
 "nope" "nope" 
text = 'The rain in Spain falls mainly in the plain.'
word_count_hash = Hash.new 0
 {} {} 
text.split(/\W+/).each { |word| word_count_hash[word.downcase] += 1 }
word_count_hash
 {"rain"=>1, "plain"=>1, "in"=>2, "mainly"=>1, "falls"=>1, {"rain"=>1, "plain"=>1, "in"=>2, "mainly"=>1, "falls"=>1, "the"=>2, "spain"=>1} 
first_letter_hash = Hash.new []
text.split(/\W+/).each { |word| first_letter_hash[word[0,1].downcase] << word }
first_letter_hash
 {} {} 
first_letter_hash["m"]
 ["The", "rain", "in", "Spain", "falls", "mainly", "in", "the", "plain"] ["The", "rain", "in", "Spain", "falls", "mainly", "in", "the", "plain"] 
first_letter_hash = Hash.new { |hash, key| hash[key] = [] }
text.split(/\W+/).each { |word| first_letter_hash[word[0,1].downcase] << word }
first_letter_hash
 {"m"=>["mainly"], "p"=>["plain"], "f"=>["falls"], "r"=>["rain"], {"m"=>["mainly"], "p"=>["plain"], "f"=>["falls"], "r"=>["rain"], "s"=>["Spain"], "i"=>["in", "in"], "t"=>["The", "the"]} 
first_letter_hash["m"]
 ["mainly"] ["mainly"]