keith/superfluous-parentheses
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version 1.0

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~keith 2022-03-13 03:50:45 +00:00
parent a3337c1ad7
commit cbf4c267df
Signed by: keith
GPG key ID: 5BEBEEAB2C73D520
2 changed files with 30 additions and 32 deletions
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10
superfluous-parentheses.asd Normal file
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;;;; superfluous-parentheses.asd
;;;; system definition file
(defsystem "superfluous-parentheses"
:description "Syntactic sugar to allow [] and {} in place of normal parentheses."
:version "1.0"
:author "keith"
:homepage "https://bytes.keithhacks.cyou/keith/superfluous-parentheses"
:license "Public Domain/CC0"
:components ((:file "superfluous-parentheses")))

52
superfluous-parentheses.lisp
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@ -4,53 +4,41 @@
(:use common-lisp))
(in-package superfluous-parentheses)
(define-condition simple-reader-error (simple-condition reader-error)
())
(defun read-bracketed-list (stream begin-char)
(let* ((end-char (cond ((char= begin-char #\[) #\])
((char= begin-char #\{) #\})
(t (error "Invalid bracket ~S" begin-char))))
(t (error 'simple-reader-error
:stream stream
:format-control "Invalid bracket ~S"
:format-arguments (list begin-char)))))
(list-body (loop for next-char = (peek-char t stream t nil t)
until (or (char= next-char end-char) (char= next-char #\.))
collect (read stream t nil t)))
(last-char (read-char stream t nil t))) ;; discard the last peeked character
(cond ((char= last-char end-char) list-body)
((char= last-char #\.)
(unless list-body
(error 'simple-reader-error
:stream stream
:format-control "Nothing before . in list."
:format-arguments nil))
;; set the CDR of the list
(rplacd (last list-body) (read stream t nil t))
;; skip past whitespace
(peek-char t stream t nil t)
(unless (char= (read-char stream t nil t) end-char)
(error "Too many objects after . in list."))
(error 'simple-reader-error
:stream stream
:format-control "Multiple objects after . in list."
:format-arguments nil))
list-body)
(t (error "Expected ~S or . but got ~S" end-char last-char)))))
#|
(declaim (special *cdr-value* *end-char*))
(defun read-bracketed-dot (stream char)
(declare (ignore char))
(let ((tail (read-delimited-list *end-char* stream t)))
(when (> (length tail) 1)
(error "Too many objects following . in list."))
(when (< (length tail) 1)
(error "Nothing appears after . in list."))
(setf *cdr-value* (car tail)))
;; put the closing bracket back, then return nothing
(unread-char *end-char* stream)
(values))
(defun read-bracketed-list (stream begin-char)
(let ((*end-char* (cond ((char= begin-char #\[) #\])
((char= begin-char #\{) #\})
(t (error "Invalid bracket ~S" begin-char))))
(*cdr-value* nil)
(*readtable* (copy-readtable)))
(set-macro-character #\. #'read-bracketed-dot t)
(let ((list-body (read-delimited-list *end-char* stream t)))
(when (and *cdr-value* (not list-body))
(error "Nothing appears before . in list."))
(rplacd (last list-body) *cdr-value*)
list-body)))
|#
(t (error 'simple-reader-error
:stream stream
:format-control "Expected ~S or ., but got ~S."
:format-arguments (list end-char last-char))))))
(set-macro-character #\[ #'read-bracketed-list)
(set-macro-character #\] (get-macro-character #\)))