function.lisp

(cl:in-package #:incf-cl)

;;; Copyright (c) 2007-2019 Juan M. Bello Rivas <jmbr@superadditive.com>
;;;
;;; Permission is hereby granted, free of charge, to any person
;;; obtaining a copy of this software and associated documentation
;;; files (the "Software"), to deal in the Software without
;;; restriction, including without limitation the rights to use, copy,
;;; modify, merge, publish, distribute, sublicense, and/or sell copies
;;; of the Software, and to permit persons to whom the Software is
;;; furnished to do so, subject to the following conditions:
;;;
;;; The above copyright notice and this permission notice shall be
;;; included in all copies or substantial portions of the Software.
;;;
;;; THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
;;; EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
;;; MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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(defun $ (&rest functions)
  "Returns the composition of FUNCTIONS.  Note that FUNCTIONS must
  be composable in the order specified.

  For example,

  INCF-CL> (funcall ($ (lambda (x) (* x x))
                       (lambda (x) (+ x 2)))
                    2)
  16

  INCF-CL> (funcall ($ #'values #'floor #'sqrt (lambda (x) (expt x 2))) -2)
  2"
  (assert (every #'functionp functions))
  (flet ((compose (f g)
           (lambda (&rest args)
             (funcall f (apply g args)))))
    (reduce #'compose functions)))

(defun canonicalize-test (test test-not)
  "Returns a validated test function for those functions that use TEST
and TEST-NOT keyword arguments."
  (let ((test (if test-not
                  (complement test-not)
                  test)))
    (check-type test function)
    test))