thinking about transducers

xf.js

var R = require('ramda');

// cf. http://thecomputersarewinning.com/post/Transducers-Are-Fundamental/

function inc(n) {
  return n + 1;
}

function meanReducer(acc, x) {
  var newAcc = {};
  newAcc.sum = acc.sum + x;
  newAcc.count = inc(acc.count);
  return newAcc;
};

console.log(R.reduce(meanReducer, {sum: 0, count: 0}, R.range(0, 10)));

// Let's try to make a transducer that will cause our mean-reducer to increment all of the inputs.
/*
(defn increment-transducer [f1]
     (fn [result input] ;; A transducer returns a reducing fn.
       (f1 result  ;; That reducing fn will still call 'f1',
         (inc input)))) ;; but only after it increments the input.
 
=> (reduce (increment-transducer mean-reducer) 
           {:sum 0 :count 0} 
           (range 10))
{:count 10, :sum 55}
*/
var incrementTransducer = function(f1) {
  return function(acc, x) {
    return f1(acc, inc(x));
  };
};

console.log(R.reduce(incrementTransducer(meanReducer), {sum: 0, count: 0}, R.range(0, 10)));