application/octet-stream
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2.30 KB
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42 lines
;;; Nujel - Copyright (C) 2020-2021 - Benjamin Vincent Schulenburg
;;; This project uses the MIT license, a copy should be included under /LICENSE
;;;
;;; The Nujel implementation for quasiquote, it is important to note that it is
;;; a macro, not a special form.
(def quasiquote (let*
(defn quasiquote-real (l depth)
(when-not l (return #nil))
(if (pair? l)
(if (= (caar l) 'unquote-splicing)
(if (zero? depth)
(list 'append
(cadr (car l))
(quasiquote-real (cdr l) depth))
(list 'unquote-splicing
(quasiquote-real (cadr l) (+ -1 depth))))
(if (= (car l) 'unquote)
(if (zero? depth)
(cadr l)
(list 'unquote
(quasiquote-real (cadr l) (+ -1 depth))))
(if (= (car l) 'quasiquote)
(quasiquote-real (quasiquote-real (cadr l) (+ 1 depth)) depth)
(if (zero? depth)
(list 'cons
(quasiquote-real (car l) depth)
(quasiquote-real (cdr l) depth))
(cons (quasiquote-real (car l) depth)
(quasiquote-real (cdr l) depth))))))
(if (and (zero? depth) (symbol? l))
(cons 'quote (cons l #nil))
l)))
(defmacro quasiquote (l)
(quasiquote-real l 0))))
(defn unquote (expr)
(throw (list :unquote-without-quasiquote "unquote should only occur inside a quasiquote, never evaluated directly")))
(defn unquote-splicing (expr)
(throw (list :unquote-splicing-without-quasiquote "unquote-splicing should only occur inside a quasiquote, never evaluated directly")))
