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

Feedback

For feedback, please check the contacts section. Before writing, please specify where you came from and who you are. Sometimes spammers go insane. Thank you in advance for your understanding.