kaku.rb

require 'test/unit'
require 'test/unit/ui/console/testrunner'

module Kaku
  FULLWIDTH_ROMAJI = '！＂＃＄％＆＇（）＊＋，－．／０１２３４５６７８９：；＜＝＞？＠ＡＢＣＤＥＦＧＨＩＪＫＬＭＮＯＰＱＲＳＴＵＶＷＸＹＺ［＼］＾＿｀ａｂｃｄｅｆｇｈｉｊｋｌｍｎｏｐｑｒｓｔｕｖｗｘｙｚ｛｜｝～　'
  HALFWIDTH_ROMAJI = '!"#$%&\'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~ '

  def fullwidth_to_halfwidth(text)
    text.gsub(/\xEF[\xBC\xBD]./) do |m|
      m[1] == 188 ?
        (m[2] - 96).chr :
        (m[2] - 32).chr
    end.gsub(/\xE3\x80\x80/, " ")
  end
end

class KakuTest < Test::Unit::TestCase

  include Kaku

  def test_fullwidth_to_halfwidth
    assert_equal(HALFWIDTH_ROMAJI, fullwidth_to_halfwidth(FULLWIDTH_ROMAJI))
  end
end

Test::Unit::UI::Console::TestRunner.run(KakuTest)