Toy implementation of Clojure 1.5's reducers library in C# (using LINQPad). https://www.clojure.org/news/2012/05/15/anatomy-of-reducer

clojure-reducer.linq

List<int> ns = new List<int> { 1, 2, 3, 4, 5, 6, 7, 8 };

Func<Func<int,int>,Func<Func<int,int,int>,Func<int,int,int>>> mapping = delegate(Func<int,int> f) {
  return (Func<int,int,int> f1) => ((int r, int i) => f1(r,f(i)));
};

Func<Func<int,bool>,Func<Func<int,int,int>,Func<int,int,int>>> filtering = delegate(Func<int,bool> pred) {
  return (Func<int,int,int> f1) => ((int r, int i) => {
    if (pred(i))
    return f1(r,i);
	else
	  return r;
  });
};

Func<int,int> half = n => n / 2;
Func<int,int> inc = n => n + 1;
Func<int,int,int> plus = (a, b) => a + b;
Func<int,bool> isEven = n => n % 2 == 0;

ns.Where(isEven).Select(half).Aggregate(0,plus).Dump("LINQ");
ns.Aggregate(0,filtering(isEven)(mapping(half)(plus))).Dump("Clojure Reducer");