Function log_returns 

pub fn log_returns(prices: &[f64]) -> FinanceResult<Vec<f64>>

Log returns for consecutive prices: length prices.len() - 1.

Examples

use finance_solution::{log_returns, FinanceError};

assert!(log_returns(&[100.0, 110.0]).is_ok());
assert!(matches!(
    log_returns(&[100.0, 0.0]),
    Err(FinanceError::InvalidCashflow { .. })
));