* is defined as the function h such that {@code h(a) == g(f(a))} for each {@code a}.
   *
   * <p><b>Java 8+ users:</b> use {@code g.compose(f)} or (probably clearer) {@code f.andThen(g)}
   * instead.
   *
   * @param g the second function to apply
   * @param f the first function to apply
   * @return the composition of {@code f} and {@code g}

   * is defined as the function h such that {@code h(a) == g(f(a))} for each {@code a}.
   *
   * <p><b>Java 8+ users:</b> use {@code g.compose(f)} or (probably clearer) {@code f.andThen(g)}
   * instead.
   *
   * @param g the second function to apply
   * @param f the first function to apply
   * @return the composition of {@code f} and {@code g}