5. Many to One: Reducing

Activity 5.01: Calculating Elo Ratings for Tennis

Solution:

1. Here is the minimal deps.edn file you'll need:

   {:deps
    {org.clojure/data.csv {:mvn/version "0.1.4"}
     semantic-csv {:mvn/version "0.2.1-alpha1"}
     org.clojure/math.numeric-tower {:mvn/version "0.0.4"}}}

2. Here is the corresponding namespace declaration:

   (ns packt-clj.elo
     (:require [clojure.math.numeric-tower :as math]
               [clojure.java.io :as io]
               [clojure.data.csv :as csv]
               [semantic-csv.core :as sc])

3. For the overall structure of your function, we will follow the same patterns we've used so far: a with-open macro with some pre-processing code:

   (defn elo-world
     ([csv k]
      (with-open...