Is it possible round up div operation for BigNumber?

[julianmrodri]

I need to round up a div operation for a BigNumber but couldnt find a way to do this.

Basically I would like BigNumber(1428571428571428571428).div(100) to round up and return for example 14285714285714285715 instead of 14285714285714285714.

Is there a way to do this? What is the best way to accomplish it in ethers.js? Should I be using FixedNumber for these type of operations?

Thanks!

[ricmoo]

Rounding is actually a far more complex topic, as there are many strategies to "break the tie", but I think what you are describing is actually finding the ceiling, which doesn't deal with tie situations.

You can absolutely use the FixedNumber class (and its .ceil method), but you can also use the following formula to compute the ceiling using integer math for positive values:

// Your specific case
BigNumber(1428571428571428571428).add(99).div(100)

// In general:
value = 1428571428571428571428
divisor = 100
BigNumber(value).add(divisor - 1).div(divisor)

For a quick check on what you want consider the following:

// Rounding (towards infinity):
> 120 / 100 => 1.2 => 1
> 150 / 100 => 1.5 => 2
> 170 / 100 => 1.7 => 2

// Ceiling:
> 120 / 100 => 1.2 => 2
> 150 / 100 => 1.5 => 2
> 170 / 100 => 1.7 => 2

Other common rounding strategies are toward-zero, away-from-zero, toward-infinity, toward-negative-infinity, truncation, toward-even, toward-odd and stochastic. Each has their specific purposes and use cases.