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;;; lib.macros.lisp - 2025-02-09
;; Copyright (C) 2025 Aryadev Chavali
;; This program is distributed in the hope that it will be useful, but WITHOUT
;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
;; FOR A PARTICULAR PURPOSE. See the GNU General Public License Version 2 for
;; details.
;; You may distribute and modify this code under the terms of the GNU General
;; Public License Version 2, which you should have received a copy of along with
;; this program. If not, please go to <https://www.gnu.org/licenses/>.
;;; Commentary:
;; Helpful macros for usage throughout the project.
;;; Code:
(in-package :cantedraw.lib.macros)
(defmacro --> (placeholder &body forms)
"Lexically bind current form as `placeholder' for use in the next form, returning
the result of the last form.
i.e.
(--> (a1 a2...) (b1 b2...) (c1 c2...)) =
(let* ((placeholder (a1 a2 ...))
(placeholder (b1 b2 ...))
(placeholder (c1 c2 ...)))
_ )
Also includes transformer where symbols are considered unary functions i.e.
(--> x y) <-> (--> x (y placeholder)).
"
(if (null forms)
nil
(let ((assignment-forms
(loop :for f :in forms
:for canon-f := (if (symbolp f)
(list f placeholder)
f)
:collect `(,placeholder ,canon-f))))
`(let* ,assignment-forms
,placeholder))))
(defmacro ->> (&rest forms)
"Make current form the last argument of the next form, returning the last
form.
i.e.
(->> (a1 a2...) (b1 b2...) (c1 c2...)) == (c1 c2 ... (b1 b2 ... (a1 a2 ...)))
Also includes transformer where symbols are considered unary functions.
Like the `|>' operator in Ocaml."
(if (null forms)
nil
(loop :with acc = (car forms)
:for func :in (cdr forms)
:for canon-func = (if (symbolp func) (list func) func)
:do (setq acc (append canon-func (list acc)))
:finally (return acc))))
(defmacro while (condition &body body)
`(loop :while ,condition
:do
(progn ,@body)))
(deftype -> (args result)
"Type alias for function."
`(function ,args ,result))
(defmacro fn (name lambda-list type &body body)
"Construct a function `NAME' with a declared function type `TYPE' that takes
arguments `LAMBDA-LIST' with body `BODY'."
`(progn
(declaim (ftype ,type ,name))
(defun ,name ,lambda-list
,@body)))
(defmacro $ (&rest forms)
"Given a sequence of FORMS, return a unary function which applies each form
sequentially"
`(lambda (x)
(->> x ,@forms)))
(defmacro alist-val (key alist)
"Helper macro for getting the value of KEY in ALIST."
`(cdr (assoc ,key ,alist)))
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