package fj.data;

import fj.F;

import fj.F1Functions;

/**

* The Reader monad (also called the function monad, so equivalent to the idea of F).

* Created by MarkPerry on 7/07/2014.

*/

public class Reader<A, B> {

private F<A, B> function;

public Reader(F<A, B> f) {

function = f;

}

public F<A, B> getFunction() {

return function;

}

public static <A, B> Reader<A, B> unit(F<A, B> f) {

return new Reader<A, B>(f);

}

public static <A, B> Reader<A, B> constant(B b) {

return unit(a -> b);

}

public B f(A a) {

return function.f(a);

}

public <C> Reader<A, C> map(F<B, C> f) {

return unit(F1Functions.andThen(function, f));

}

public <C> Reader<A, C> andThen(F<B, C> f) {

return map(f);

}

public <C> Reader<A, C> flatMap(F<B, Reader<A, C>> f) {

return unit(a -> f.f(function.f(a)).f(a));

}

public <C> Reader<A, C> bind(F<B, Reader<A, C>> f) {

return flatMap(f);

}

}