Question

test = 'a'
test2 = '@a'.slice(0)
test3 = '@a'[1]

puts test.hash
puts test2.hash
puts test3.hash

Output:

100
64
97

Is this a bug or am I misunderstanding how the hash method works? Is there a way to fix this?

Answer 1

The results of these expressions are not all the same data. Ruby 1.8 integers contain character numbers for single character indexing. This has been changed in Ruby 1.9, but slice(0) returns the first character of the string '@', not 'a'.

In Ruby 1.8 (using irb):

irb(main):001:0> test = 'a'
=> "a"
irb(main):002:0> test2 = '@a'.slice(0)
=> 64
irb(main):003:0> test3 = '@a'[1]
=> 97
irb(main):004:0> test.hash
=> 100
irb(main):005:0> test2.hash
=> 129
irb(main):006:0> test3.hash
=> 195

In Ruby 1.9.1:

irb(main):001:0> test = 'a'
=> "a"
irb(main):002:0> test2 = '@a'.slice(0)
=> "@"
irb(main):003:0> test3 = '@a'[1]
=> "a"
irb(main):004:0> test.hash
=> 1365935838
irb(main):005:0> test2.hash
=> 347394336
irb(main):006:0> test3.hash
=> 1365935838