Can anybody please tell me how to set or reset a bit in lua..?

Question

I want to perform set and reset of particular bit in a number. As I'm using lua 5.1 I can't able to use APIs and shifting operators so it is becoming more and more complex so please help me finding this

Answer 1

bit library is shipped with the firmware.

Read the documentation: https://nodemcu.readthedocs.io/en/release/modules/bit/

Answer 2

You can do it without external libraries, if you know the position of the bit you wish to flip.

#! /usr/bin/env lua

local hex  = 0xFF
local maxPos  = 7

local function toggle( num, pos )
    if pos < 0 or pos > maxPos then print( 'pick a valid pos, 0-' ..maxPos )
    else
        local bits = {}  --  populate emtpy table
        for i=1, maxPos do bits[i] = false end

        for i = maxPos, pos +1, -1 do  --  temporarily throw out the high bits
            if num >= 2 ^i then
                num = num -2 ^i
                bits [i +1] = true
            end
         end

        if num >= 2 ^pos then  num = num -2 ^pos  -- flip desired bit
        else                   num = num +2 ^pos
        end

        for i = 1, #bits do  --  add those high bits back in
            if bits[i] then num = num +2 ^(i -1) end
        end

    end ; print( 'current value:', num )
    return num
end

original value: 255
current value: 127
pick a valid pos, 0-7
current value: 127
current value: 255