troyp/fn.el

Concise anonymous functions for Emacs Lisp

fn.el -- Concise anonymous functions for Emacs Lisp.

fn.el provides macros for writing concise and readable anonymous functions.

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Installation

• Install from melpa using M-x list-packages.

• Or, place fn.el in any directory on your load-path and execute:

  (require 'fn)

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API

• fn (&rest body)
• fn: (&rest body)

fn (&rest BODY)

Return a function defined by BODY.

Intended for inline use where concision is desired. If creating a function to bind as a function value, use lambda or -lambda.

The definition BODY may use anaphoric parameters to refer to the arguments. For a single-argument function, <> can be used. For a multiple-argument function, use <1> to refer to the first argument, <2> to refer to the second, and so on up to <9>. The parameter <rest> refers to a list containing the (n+1)st and later arguments, where <n> is the highest numerical parameter supplied.

If applied to a literal, creates a constant function, or equivalently, a thunk (since it can be called with any number of arguments).

(-map (fn (* <> <>)) (number-sequence 0 10))
;; (0 1 4 9 16 25 36 49 64 81 100)

(-map (fn (/ (-sum <>)
            (length <>)))
      '((3.0 4.0 5.0 5.0 10.0)
        (1.5 2.5 2.0)
        (1 5)))
;; (5.4 2.0 3)
;; find average of each list

(-filter (fn (zerop (mod <> 3)))
        (number-sequence 1 10))
;; (3 6 9)

(funcall (fn 7))
;; 7

(funcall (fn (-map #'list <rest>)) 1 2 3 4)
;; ((1) (2) (3) (4))

fn: (&rest BODY)

Return a function defined by (BODY).

Intended for inline use where concision is desired. If creating a function to bind as a function value, use lambda or -lambda.

Identical to fn except that BODY is automatically parenthesized.

The definition BODY may use the anaphoric parameter <> for the sole argument, or <1> ... <9> to refer to multiple positional arguments. The parameter <rest> refers to a list containing the (n+1)st and later arguments, where <n> is the highest numerical parameter supplied.

(-map (fn: * <> <>) (number-sequence 0 10))
;; (0 1 4 9 16 25 36 49 64 81 100)

(-filter (fn: > <> 0)
        '(-5 2 0 0 3 -1 0 4))
;; (2 3 4)

fn.el's Issues

helper to create (interactive ...) functions

...so that fn.el can be used as a substitute for (lambda () (interactive) (do-something 'very 'special)), e.g. for use with define-key.