--[[
Eugeniy Mikhailov
1 June 2021
 ]]
------------ BITS TO DECIMAL ------------ 
function toNum(bits)
	local n = 0; local m = 1 -- m represents power of 2
	for i = 1, #bits do -- '#' indicates number of bits in variable
	  n = n + bits[i]*m
	  m = m*2
    end
	return n
end


------------ DECIMAL TO BIT ------------ 
-- ****NOTE: Suitable only for positive integer inputs****
-- continue to divide by two until quotient is zero
function toBits(num)    
    local t = {}
    local cnt = 0
    while num > 0 do
	cnt = cnt + 1
        remainder = num % 2 -- Basics of binary. If num is divisible by two, 0 in table. If not, 1 in table
        t[cnt] =  remainder -- defaults to #t+1 key
        num = (num - remainder)/2
        --num = math.floor((num - remainder)/2) -- carry out calculation
            -- note math.floor used here to eliminate floating values
        --we subtract the number with the binary bit found, then divide by two to find the next bit
    end
    return t
end

------------ BINARY SEPARATION TO STRING ------------ 
function bin2string(bTable, separator)
    if  nil == separator then separator="" end
    local str=""
    for i=#bTable,1,-1 do
        if (i % 8) == 0 then str=str..separator end -- space between every 8 bits
        if bTable[i] == 0 -- to take care of floats
        then
            str=str.."0"
        else 
            str=str.."1" -- assumes only nonzeros are ones
                -- if nonzeros/ones involved, will also be counted as ones here
        end
    end
    return str
end

------------ TESTS FOR bin2string------------ 
if "11111110" ~= bin2string(toBits(254))
then
    print("Error in bits conversion")
end
if 2376 ~= toNum(toBits(2376))
then
    print("Error in bits conversion")
end

------------ SLICE STRING ------------
function bitSlice(bTable, low, high)
    -- make sure that 1 <= low <= high
    local slice={}
    local cnt=1 --counter
    for i=low,high
    do
        slice[cnt] = (bTable[i])
        cnt = cnt+1
    end
    return slice
end

------------ TESTS FOR bitSlice ------------ 
if "345" ~= table.concat(bitSlice({1,2,3,4,5,6,7,8}, 3,5))
then
    print("Error bitSlice is compromised")
end

------------ COPY TABLE ------------
-- issue with index naming in future table. 
function copyTableArray(src)
    local dst={}
    for i=1,#src do
        dst[i] = (src[i])
    end
    return dst
end

------------ COMBINE SLICES ------------
function tableReplace(bTable1, bTable2, low, high) -- low=first index, high=last index
    local dest = copyTableArray(bTable1)
    local cnt=1
    for i=low,high do
        dest[i]=(bTable2[cnt])
        cnt = cnt + 1
    end
    return dest -- destination
end

------------ PAD ZEROS INTO EMPTY INDICES ------------
function pad2NumBitsInPlace(bTable, num)
    for i= #bTable+1, num do
        bTable[i]=0
    end
    return bTable
end

------------ TEST PAD ZEROS ------------
if "00010111" ~= bin2string(pad2NumBitsInPlace({1,1,1,0,1},8))
then
    print("Error in pad2NumBitsInPlace")
end