48 lines
2.1 KiB
Common Lisp
48 lines
2.1 KiB
Common Lisp
;;;; superfluous-parentheses.lisp
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;;;; Adds support for [] and {} in place of normal parentheses
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(defpackage superfluous-parentheses
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(:use common-lisp))
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(in-package superfluous-parentheses)
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(define-condition simple-reader-error (simple-condition reader-error)
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())
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(defun read-bracketed-list (stream begin-char)
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(let* ((end-char (cond ((char= begin-char #\[) #\])
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((char= begin-char #\{) #\})
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(t (error 'simple-reader-error
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:stream stream
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:format-control "Invalid bracket ~S"
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:format-arguments (list begin-char)))))
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(list-body (loop for next-char = (peek-char t stream t nil t)
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until (or (char= next-char end-char) (char= next-char #\.))
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collect (read stream t nil t)))
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(last-char (read-char stream t nil t))) ;; discard the last peeked character
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(cond ((char= last-char end-char) list-body)
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((char= last-char #\.)
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(unless list-body
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(error 'simple-reader-error
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:stream stream
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:format-control "Nothing before . in list."
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:format-arguments nil))
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;; set the CDR of the list
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(rplacd (last list-body) (read stream t nil t))
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;; skip past whitespace
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(peek-char t stream t nil t)
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(unless (char= (read-char stream t nil t) end-char)
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(error 'simple-reader-error
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:stream stream
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:format-control "Multiple objects after . in list."
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:format-arguments nil))
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list-body)
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(t (error 'simple-reader-error
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:stream stream
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:format-control "Expected ~S or ., but got ~S."
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:format-arguments (list end-char last-char))))))
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(set-macro-character #\[ #'read-bracketed-list)
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(set-macro-character #\] (get-macro-character #\)))
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(set-macro-character #\{ #'read-bracketed-list)
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(set-macro-character #\} (get-macro-character #\)))
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