Binary search for Lua 5.x

binSearch.lua

do
  local floor = math.floor
  ---@param tbl any[]
  ---@param value any
  ---@param iStart integer?
  ---@param iEnd integer?
  ---@param reversed boolean?
  ---@return any?
  function binSearch(tbl, value, iStart, iEnd, reversed)
    --  Initialise numbers
    iStart, iEnd = iStart or 1, iEnd or #tbl
    local iMid = 0
    if reversed then
      -- Reversed Binary Search
      while iStart <= iEnd do
        -- calculate middle
        iMid = floor( (iStart+iEnd) / 2 )
        -- get compare value
        local value2 = tbl[iMid]
        -- get all values that match
        if value == value2 then
            return iMid 
        -- keep searching
        elseif value > value2 then
            iEnd = iMid - 1
        else
            iStart = iMid + 1
        end
      end
    else
      -- Binary Search
      while iStart <= iEnd do
        -- calculate middle
        iMid = floor( (iStart+iEnd) / 2 )
        -- get compare value
        local value2 = tbl[iMid]
        -- get all values that match
        if value == value2 then
            return iMid 
        -- keep searching
        elseif value < value2 then
            iEnd = iMid - 1
        else
            iStart = iMid + 1
        end
      end
    end
  end
end