More lib files, more functional

Still missing that 'attack' fn, though :(

lib/reducers.ts

@@ -0,0 +1,10 @@
+export const pipe = (...fns) => (input) =>
+  fns.reduce((acc, fn) => fn(acc), input);
+
+export const redFn = (acc, x) => [...acc, x];
+
+export const mapR = (fn) => (input) =>
+  input.reduce((acc, x) => [...acc, fn(x)], []);
+
+export const filterR = (pred) => (input) =>
+  input.reduce((acc, x) => pred(x) ? [...acc, x] : acc ,[]);