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"]]]
