exchange is:exact

O(1) Replace the element at a given type-safe position and return the old element, using Finite.
O(1) Replace the element at a given type-safe position and return the old element, using Finite.
O(1) Replace the element at a given type-safe position and return the old element, using Finite.
O(1) Replace the element at a given type-safe position and return the old element, using Finite.
O(1) Replace the element at a given type-safe position and return the old element, using Finite.
Apply the ExchangeRate to the given Dense src monetary value. Identity law:
exchange (exchangeRateRecip x) . exchange x  ==  id
Use the Identity law for reasoning about going back and forth between src and dst in order to manage any leftovers that might not be representable as a Discrete monetary value of src.
Perform the initial credentials exchange to obtain a valid OAuthToken suitable for authorizing requests.