Merge commit '47f60d0996ed57d3a3c00b25ddbd8fea04096f90' as 'third_party/lisp/quasiquote_2' r/450

1 files changed, 77 insertions, 0 deletions

diff --git a/third_party/lisp/quasiquote_2/readers.lisp b/third_party/lisp/quasiquote_2/readers.lisp
new file mode 100644
index 000000000000..7c4c5a30c98e
--- /dev/null
+++ b/third_party/lisp/quasiquote_2/readers.lisp
@@ -0,0 +1,77 @@
+
+
+(in-package #:quasiquote-2.0)
+
+(defun read-n-chars (stream char)
+  (let (new-char
+	(n 0))
+    (loop
+       (setf new-char (read-char stream nil :eof t))
+       (if (not (char= new-char char))
+	   (progn (unread-char new-char stream)
+		  (return n))
+	   (incf n)))))
+
+(defmacro define-dig-reader (name symbol)
+  `(defun ,name (stream char)
+     (let ((depth (1+ (read-n-chars stream char))))
+       (if (equal 1 depth)
+	   (list ',symbol (read stream t nil t))
+	   (list ',symbol
+		 depth
+		 (read stream t nil t))))))
+
+(define-dig-reader dig-reader dig)
+(define-dig-reader odig-reader odig)
+
+(defun expect-char (char stream)
+  (let ((new-char (read-char stream t nil t)))
+    (if (char= char new-char)
+	t
+	(unread-char new-char stream))))
+
+(defun guess-injector-name (opaque-p macro-p all-p splicing-p)
+  (intern (concatenate 'string
+		       (if opaque-p "O" "")
+		       (if macro-p "MACRO-" "")
+		       (if splicing-p "SPLICE" "INJECT")
+		       (if all-p "-ALL" ""))
+	  "QUASIQUOTE-2.0"))
+
+(defun inject-reader (stream char)
+  (let ((anti-depth (1+ (read-n-chars stream char)))
+	(extended-syntax (expect-char #\! stream)))
+    (let ((injector-name (if (not extended-syntax)
+			     (guess-injector-name nil nil nil (expect-char #\@ stream))
+			     (guess-injector-name (expect-char #\o stream)
+						  (expect-char #\m stream)
+						  (expect-char #\a stream)
+						  (expect-char #\@ stream)))))
+      `(,injector-name ,@(if (not (equal 1 anti-depth)) `(,anti-depth))
+		       ,(read stream t nil t)))))
+
+
+
+(defvar *previous-readtables* nil)
+
+(defun %enable-quasiquote-2.0 ()
+  (push *readtable*
+        *previous-readtables*)
+  (setq *readtable* (copy-readtable))
+  (set-macro-character #\` #'dig-reader)
+  (set-macro-character #\, #'inject-reader)
+  (values))
+
+(defun %disable-quasiquote-2.0 ()
+  (if *previous-readtables*
+      (setf *readtable* (pop *previous-readtables*))
+      (setf *readtable* (copy-readtable nil)))
+  (values))
+
+(defmacro enable-quasiquote-2.0 ()
+  `(eval-when (:compile-toplevel :load-toplevel :execute)
+     (%enable-quasiquote-2.0)))
+(defmacro disable-quasiquote-2.0 ()
+  `(eval-when (:compile-toplevel :load-toplevel :execute)
+     (%disable-quasiquote-2.0)))
+