[naseweisssss]

Add some documentations in relation to issues #130 to clarify the usage of signs on fv and pv

[InessaPawson]

Thanks for working on this, @naseweisssss !
The zero rate example is a great idea, it's much easier to do the math. I checked against the implementation, and it's right.
A few small requests:

1. Keep "Future value" as the term for fv. That is the terminology used throughout the API: pv, nper, ipmt, ppmt, rate - all document the fv parameter as “Future value”. Also, fv itself is defined as computing the future value. Renaming it only in pmt would introduce an inconsistency.
2. Make the pv note perspective-independent, e.g., "Cash received is positive and cash paid out is negative. For a borrower, the loan amount is positive".
3. ipmt, ppmt, nper, and fv share the same convention and descriptions. A short note in the module docstring explaining the convention would be nice. Also could be a follow-up PR.

[naseweisssss]

Thanks for working on this, @naseweisssss ! The zero rate example is a great idea, it's much easier to do the math. I checked against the implementation, and it's right. A few small requests:

1. Keep "Future value" as the term for fv. That is the terminology used throughout the API: pv, nper, ipmt, ppmt, rate - all document the fv parameter as “Future value”. Also, fv itself is defined as computing the future value. Renaming it only in pmt would introduce an inconsistency.
2. Make the pv note perspective-independent, e.g., "Cash received is positive and cash paid out is negative. For a borrower, the loan amount is positive".
3. ipmt, ppmt, nper, and fv share the same convention and descriptions. A short note in the module docstring explaining the convention would be nice. Also could be a follow-up PR.

Thanks for the comments,

1. I have changed it back to Future value.
2. Used the recommended wording
3. add on top of the module docstring

[InessaPawson]

Thanks for the quick turnaround, @naseweisssss! All requests from my review are addressed, so it’s Approve from me.

@stefanv I believe this is ready to be merged.

[seberg]

Thanks, this seems sensible to me and I don't have thoughts on bikeshedding things more. The one thing I feel more generally, is that using kwargs might be clearer, but they don't even have that nice names :).

[naseweisssss]

Thanks, this seems sensible to me and I don't have thoughts on bikeshedding things more. The one thing I feel more generally, is that using kwargs might be clearer, but they don't even have that nice names :).

Thanks, it doesnt look like I can merge this still.

[seberg]

A maintainer needs to merge :). Thanks @naseweisssss!