Ruby: Count Unique Consonants

Using array intersection to count unique consonants.

Interactive Ruby Shell

irb(main):001:0> s = 'dRGgr90xy'
=> "dRGgr90xy"
irb(main):002:0> con = ["b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z"]
=> ["b", "c", "d", "f", "g", "h", "j", "k", "l", "m", "n", "p", "q", "r", "s", "t", "v", "w", "x", "y", "z"]
irb(main):003:0> a = s.downcase
=> "drggr90xy"
irb(main):004:0> a = a.split('')
=> ["d", "r", "g", "g", "r", "9", "0", "x", "y"]
irb(main):005:0> (con & a).length
=> 5

In the Ruby REPL demonstration above, unique consonants are found by intersecting an array containing all consonants with a string passed to the function count_consonants(). That string passed to the function is first converted to all lowercase letters, then split into an array containing separate character strings which are finally counted, e.g. 5.

Reference

Set Intersection in Ruby