Module:Exponential search

-- This module provides a generic exponential search algorithm.

local checkType = require('libraryUtil').checkType local floor = math.floor

local function midPoint(lower, upper) return floor(lower + (upper - lower) / 2) end

local function search(testFunc, i, lower, upper) if testFunc(i) then if i + 1 == upper then return i end lower = i if upper then i = midPoint(lower, upper) else i = i * 2 end return search(testFunc, i, lower, upper) else upper = i i = midPoint(lower, upper) return search(testFunc, i, lower, upper) end end

return function (testFunc, init) checkType('Exponential search', 1, testFunc, 'function') checkType('Exponential search', 2, init, 'number', true) if init and (init < 1 or init ~= floor(init) or init == math.huge) then error(string.format( "invalid init value '%s' detected in argument #2 to " .. "'Exponential search' (init value must be a positive integer)", tostring(init) ), 2) end init = init or 2 if not testFunc(1) then return nil end return search(testFunc, init, 1, nil) end