#+title: functional application

Functional application is the act of applying arguments to a [[file:20210521211721-function_programming.org][function]]. In
programming this is usually distinct from simply calling a function.

In a [[file:20200604222651-lisp.org][Lisp]], usually this means taking an actual list of arguments and calling a
function with it:

#+begin_src emacs-lisp
(apply 'car '((1 2 3)))
#+end_src

#+RESULTS:
: 1

Compare that with:

#+begin_src emacs-lisp
(car '(1 2 3))
#+end_src

#+RESULTS:
: 1

In the first instance, the outer list is supplying the list of arguments to
=car=.

In [[file:20200604222651-lisp.org][Lisp]], functional application is the cornerstone of a Lisp interpreter, where
often in the source code a function's arguments are quite literally applied to
it.

Or, consider the following in [[file:20200720132835-javascript.org][JavaScript]]:

#+begin_src js :results output
const add = (x, y, z) => x + y + z;
console.log(add.apply(null, [1, 2, 3]));
#+end_src

#+RESULTS:
: 6