BigNumber.pow doesn't work for negative numbers

[rhlsthrm]

> eth.utils.parseEther('1').mul(eth.BigNumber.from(10).pow(0)).toString()
'1000000000000000000'
> eth.utils.parseEther('1').mul(eth.BigNumber.from(10).pow(-8)).toString()
'100000000000000000000000000'
> eth.utils.parseEther('1').mul(eth.BigNumber.from(10).pow(8)).toString()
'100000000000000000000000000'

Does the function silently use absolute value?

[ricmoo]

That seems like what is happening in your above example and this is certainly a bug. I’ll address it ASAP.

Thanks!

[ricmoo]

It seems negative values are not supported, in general, by BN.js, which kind makes sense in the context of a big number library.

I think the solution will be throwing in the event there is a negative exponent.

Looking more closely at what you are trying to do above, the result you would expect is 0 though. Consider:

// BigNumbers do not support fractions, so this would be 0.00000001, which is 0 to a BigNumber
const a = eth.BigNumber.from(10).pow(-8);

// This times 0 is 0
const b = eth.utils.parseEther('1').mul(a);

What you more likely want to do is use the parseUnits (or if you wish more control, the FixedNumber class directly):

const b = eth.utils.parseUnits("1", 18 - 8).toString();
// "10000000000"

[ricmoo]

This has been addressed in 5.0.4.

I don't know it will help you the way you want it to, but the FixedNumber and and parseUnits should help you. :)

[ricmoo]

Closing this now, but if you still have problems, please re-open this issue.

Thanks! :)