For those that have a hard time reading the clojure code, i recomend this blogpost where they are explained with js. See: http://phuu.net/2014/08/31/csp-and-transducers.html
That article was what inspired me to write this blog post.
In short, the key insight of the blog post is this (via untested javascript):
You can define transforming functions like map and filter via reduce (e.g. foldleft or, for Ruby, inject) instead. For example,
map([...], function (x) { return x + 1; });
// append (x + 1) to the result collection
reduce([...], [], function (result, x) { return append(result, plusOne(x)); });
function mapping(f) {
return function (reducing) {
return function (result, input) {
return reducing(result, f(input));
}
};
}
var xform = mapping(plusOne)(append);
reduce([...], [], xform);