Function nper_solution 

pub fn nper_solution<C, P, F>(
    periodic_rate: f64,
    payment: C,
    present_value: P,
    future_value: F,
) -> FinanceResult<NperSolution>
where
    C: Into<f64> + Copy,
    P: Into<f64> + Copy,
    F: Into<f64> + Copy,

nper with a solution struct (formula string + inputs).

Errors

Same domain rules as nper.