Module:Exponential search

-- This module provides a generic binary 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 binarySearch(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 binarySearch(testFunc, i, lower, upper) else upper = i		lower = lower or 0 i = midPoint(lower, upper) return binarySearch(testFunc, i, lower, upper) end end

return function (testFunc, init) checkType('Binary search', 1, testFunc, 'function') checkType('Binary search', 2, initNum, 'number', true) if init then if init < 1 or init ~= floor(init) or init == math.huge or tostring(init) == '-nan' then error("if an init is specified to 'Binary search', it must be a positive integer", 2) end else init = 1 end if not testFunc(1) then return nil end return binarySearch(testFunc, init) end