pangram_bench.rb

require 'benchmark/ips'

class PangramArraySubtraction
  def self.pangram?(phrase)
    ([*'a'..'z'] - phrase.downcase.chars).empty?
  end
end

class PangramArrayAllInclude
  def self.pangram?(phrase)
    phrase.downcase.chars.all?(&('a'..'z').method(:include?))
  end
end

class PangramAllSquareBrackets
  def self.pangram?(phrase)
    ('a'..'z').all?(&phrase.downcase.method(:[]))
  end
end

module PangramAllHash
  ALPHABET = ('a'..'z')
  def self.pangram?(phrase)
    return false if phrase.empty?
    phrase_hash = phrase_hash(phrase)
    ALPHABET.all?(&phrase_hash.method(:[]))
  end

  def self.phrase_hash(phrase)
    phrase.chars.reduce({}) do |hash, letter|
      hash[letter.downcase] ||= true
      hash
    end
  end
end

phrases = [
  '',
  'abcdefghijklmnopqrstuvwxyz',
  'the quick brown fox jumps over the lazy dog',
  'a quick movement of the enemy will jeopardize five gunboats',
  'five boxing wizards jump quickly at it',
  'the_quick_brown_fox_jumps_over_the_lazy_dog',
  'the 1 quick brown fox jumps over the 2 lazy dogs',
  '7h3 qu1ck brown fox jumps ov3r 7h3 lazy dog',
  '"Five quacking Zephyrs jolt my wax bed."',
  'the quick brown fox jumps over with lazy FX',
]
Benchmark.ips do |x|
  x.config(:time => 5, :warmup => 2)

  x.report("PangramArraySubtraction") do
    phrases.each{ |phrase| PangramArraySubtraction.pangram?(phrase) }
  end
  x.report("PangramArrayAllInclude") do
    phrases.each{ |phrase| PangramArrayAllInclude.pangram?(phrase) }
  end
  x.report("PangramAllSquareBrackets") do
    phrases.each{ |phrase| PangramAllSquareBrackets.pangram?(phrase) }
  end
  x.report("PangramAllHash") do
    phrases.each{ |phrase| PangramAllHash.pangram?(phrase) }
  end

  x.compare!
end

Calculating -------------------------------------
PangramArraySubtraction
                          8.826k (± 1.5%) i/s -     44.523k in   5.045625s
PangramArrayAllInclude
                         14.644k (± 1.6%) i/s -     74.205k in   5.068475s
PangramAllSquareBrackets
                         19.093k (± 1.5%) i/s -     96.876k in   5.075205s
      PangramAllHash      4.384k (± 3.3%) i/s -     22.250k in   5.081523s

Comparison:
PangramAllSquareBrackets:    19092.7 i/s
PangramArrayAllInclude:      14644.1 i/s - 1.30x  slower
PangramArraySubtraction:      8826.0 i/s - 2.16x  slower
      PangramAllHash:         4383.7 i/s - 4.36x  slower