geohash_encode_refactoring.rb

# リファクタリング前
  def encode(latitude, longitude, precision=12)
    lat = [-90.0, 90.0]
    lng = [-180.0, 180.0]
    
    is_even = true
    bit = ch = 0
    geohash = ""
    while geohash.length < precision do
      point = is_even ? lng : lat
      mid = (point[0] + point[1]) / 2
      if (is_even ? longitude : latitude) > mid
        ch |= BITS[bit]
        point[0] = mid
      else
        point[1] = mid
      end
      
      is_even = !is_even
      if bit < 4
        bit += 1
      else
        geohash << BASE32[ch,1]
        ch = bit = 0
      end
    end
    
    geohash
  end

# リファクタリング後
  def encode(latitude, longitude, precision=12)
    latlng = [latitude, longitude]
    points = [[-90.0, 90.0], [-180.0, 180.0]]
    is_lng = 1
    (0...precision).map {
      ch = 0
      5.times do |bit|
        mid = (points[is_lng][0] + points[is_lng][1]) / 2
        points[is_lng][latlng[is_lng] > mid ? 0 : 1] = mid
        ch |=  BITS[bit] if latlng[is_lng] > mid
        is_lng ^= 1
      end
      BASE32[ch,1]
    }.join
  end

# 共通
  BITS = [16, 8, 4, 2, 1]
  BASE32 = "0123456789bcdefghjkmnpqrstuvwxyz"