chebyshev distance


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by Yonaba

in lua

Source Code

-- Chebyshev distance distance implementation
-- See: http://en.wikipedia.org/wiki/Chebyshev_distance

-- Returns the Chebyshev distance between two vectors
-- p       : a first vector
-- q       : a second vector
-- returns : the distance between p and q
local function chebyshev_distance(p, q)
  assert(#p == #q, 'vectors must have the same length')
  local d = 0
  for i in ipairs(p) do
    d = math.max(d, math.abs(p[i] - q[i]))
  end
  return d
end

return chebyshev_distance
-- Tests for chebyshev_distance.lua
local cdist = require 'chebyshev_distance'

local total, pass = 0, 0

local function dec(str, len)
  return #str < len
     and str .. (('.'):rep(len-#str))
      or str:sub(1,len)
end


local function run(message, f)
  total = total + 1
  local ok, err = pcall(f)
  if ok then pass = pass + 1 end
  local status = ok and 'PASSED' or 'FAILED'
  print(('%02d. %68s: %s'):format(total, dec(message,68), status))
end

-- Fuzzy equality test
local function fuzzyEqual(a, b)
  return math.abs(a-b) < 1e-8
end

run('Chebyshev distance test', function()
  assert(cdist({},{}), 0)
  assert(cdist({1,2,3},{4,5,6}), 3)
  assert(cdist({1,2,-1},{4,4,6}), 7)
  assert(not pcall(cdist,{1,2,3},{4,5}))
end)

print(('-'):rep(80))
print(('Total : %02d: Pass: %02d - Failed : %02d - Success: %.2f %%')
  :format(total, pass, total-pass, (pass*100/total)))