add log_product

[cscherrer]

This PR adds log_product:

pub fn log_product(data: impl Iterator<Item = f64>) -> f64 {
    let mut result = 0.0;
    let mut prod = 1.0;
    for x in data {
        let next_prod: f64 = x * prod;
        if next_prod.is_normal() {
            prod = next_prod;
        } else {
            if x.is_zero() {
                return f64::NEG_INFINITY;
            }
            result += prod.ln();
            prod = x;
        }
    }
    result + prod.ln()
}

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.38%. Comparing base (b5395e9) to head (b3501b4).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #7      +/-   ##
==========================================
+ Coverage   81.34%   81.38%   +0.04%     
==========================================
  Files          90       90              
  Lines       18255    18305      +50     
  Branches    18255    18305      +50     
==========================================
+ Hits        14849    14898      +49     
- Misses       3280     3281       +1     
  Partials      126      126              

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[BaxterEaves]

LGTM! Thanks for all the tests