[Currency Exchange] Inconsistent change value type (`float`/`int`)

Exchanged value is of type float:

https://github.com/exercism/python/blob/48e47c1f6af8050e135747461085d713a3231164/exercises/concept/currency-exchange/exchange.py#L6

Remaining value is of type float as well:

https://github.com/exercism/python/blob/48e47c1f6af8050e135747461085d713a3231164/exercises/concept/currency-exchange/exchange.py#L17

Value exchangeable in bills of a certain denomination is of type int, but that is justifiable because denominations are integers:

https://github.com/exercism/python/blob/48e47c1f6af8050e135747461085d713a3231164/exercises/concept/currency-exchange/exchange.py#L52

However, non-exchangeable value is of type int as well, which I believe is inconsistent:

https://github.com/exercism/python/blob/48e47c1f6af8050e135747461085d713a3231164/exercises/concept/currency-exchange/exchange.py#L65

Given the established structure, I see no reason why the non-exchangeable value should be integer. I mean, it clearly is not integer, but has to be rounded artificially to pass the tests.

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Overall, I was surprised how convoluted this seemingly simple exercise was.

For one, there are few opportunities to reuse code in exchangeable_value (task 5) and non_exchangeable_value (task 6). The essence of both of these functions is to calculate the exchangeable amount given the spread, which could’ve been implemented in exchange_money (task 1). Then exchangeable_value could potentially reuse get_value_of_bills (task 3), whereas non_exchangeable_value could potentially reuse get_change (task 2) – except for the fact that it expects an integer, therefore this issue.

As a side note, if we’re really looking to encourage the usage of the modulo operator %, we could introduce a task to convert amounts using different denominations (and e.g. calculate the remainder that cannot be converted).

Happy to discuss & potentially submit a PR.

[pranasziaukas]

Hello and thanks for your thoughtful (as always) response @BethanyG.

Just let me know how you’d like to proceed - I am open to revamp, replacement, and/or extension.

Since I’m still an infrequent visitor, not really comfortable to do a deep strategic dive. I will iterate the current exercise to hopefully make things more consistent and friendly to further changes.

PR incoming!

[pranasziaukas]

Sorry, I still intend to circle back to this @BethanyG. I opened this issue just before my vacation thinking I might have some spare time while traveling, but I was wrong 😃