Rounding a number to step

Rounding integers to a given step is a very common task, often it is asked at technical interviews and very often such a task appears in daily jobs.

Algorithm

1. (optional) Subtract offset from x; text x = x - offset
2. divide step #1 value by step; text x = x / step
3. (optional) to make it work like a round function, then add to the step #3 value 0.5; text x = x + 0.5
4. apply math.ceil function to step #3 value, text x = ceil(x)
5. multiply step #2 value by step; text x = x * 2
6. (optional) After adding an offset to the final result. text x = x + offset

Function for the rounding

---@param n number
---@param step number
---@param offset? number is added to the result
local function round(x, step, offset)
    offset = offset or 0
    return math.ceil((x - offset) / step + 0.5) * step + offset
end

Examples

print(round(-643, 50)) --> -650
print(round(-117, 10, 10)) --> -120
print(round(-113, 10)) --> -110
print(round(0, 10)) --> 0
print(round(9, 10)) --> 10
print(round(10, 10)) --> 10
print(round(133, 20)) --> 140
print(round(122, 20)) --> 120
print(round(134, 50)) --> 150
print(round(1123, 50)) -->1100