arc3.1.tar

1 files changed, 48 insertions, 0 deletions

diff --git a/brackets.scm b/brackets.scm
new file mode 100644
index 0000000..fa52a53
--- /dev/null
+++ b/brackets.scm
@@ -0,0 +1,48 @@
+; From Eli Barzilay, eli@barzilay.org
+
+;> (require "brackets.scm") 
+;> (use-bracket-readtable) 
+;> ([+ _ 1] 10) 
+;11
+
+(module brackets mzscheme
+  
+; main reader function for []s
+; recursive read starts with default readtable's [ parser,
+; but nested reads still use the curent readtable:
+
+(define (read-square-brackets ch port src line col pos)
+  `(fn (_)
+     ,(read/recursive port #\[ #f)))
+  
+; a readtable that is just like the builtin except for []s
+
+(define bracket-readtable
+  (make-readtable #f #\[ 'terminating-macro read-square-brackets))
+  
+; call this to set the global readtable
+
+(provide use-bracket-readtable)
+
+(define (use-bracket-readtable)
+  (current-readtable bracket-readtable))
+  
+; these two implement the required functionality for #reader
+    
+;(define (*read inp)
+;  (parameterize ((current-readtable bracket-readtable))
+;    (read inp)))
+
+(define (*read . args)
+  (parameterize ((current-readtable bracket-readtable))
+    (read (if (null? args) (current-input-port) (car args)))))
+
+(define (*read-syntax src port)
+  (parameterize ((current-readtable bracket-readtable))
+    (read-syntax src port)))
+
+; and the need to be provided as `read' and `read-syntax'
+
+(provide (rename *read read) (rename *read-syntax read-syntax))
+
+)