add annotation module

* module/ice-9/annotate.scm: Add annotation module, for source location
  tracking with syncase, and for internal use in the compiler.

module/ice-9/annotate.scm

@@ -0,0 +1,54 @@
+;;;; 	Copyright (C) 2009 Free Software Foundation, Inc.
+;;;; 
+;;;; This library is free software; you can redistribute it and/or
+;;;; modify it under the terms of the GNU Lesser General Public
+;;;; License as published by the Free Software Foundation; either
+;;;; version 2.1 of the License, or (at your option) any later version.
+;;;; 
+;;;; This library is distributed in the hope that it will be useful,
+;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+;;;; Lesser General Public License for more details.
+;;;; 
+;;;; You should have received a copy of the GNU Lesser General Public
+;;;; License along with this library; if not, write to the Free Software
+;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+;;;; 
+
+
+(define-module (ice-9 annotate)
+  :export (<annotation> annotation? annotate make-annotation
+           annotation-expression annotation-source annotation-stripped
+           set-annotation-stripped!))
+
+(define <annotation>          
+  (make-vtable "prprpw"
+               (lambda (struct port)
+                 (display "#<annotation of ")
+                 (display (struct-ref 0))
+                 (display ">"))))
+
+(define (annotation? x)
+  (and (struct? x) (eq? (struct-vtable x) <annotation>)))
+
+(define (make-annotation e s stripped?)
+  (make-struct <annotation> 0 e s stripped?))
+
+(define (annotation-expression a)
+  (struct-ref a 0))
+(define (annotation-source a)
+  (struct-ref a 1))
+(define (annotation-stripped a)
+  (struct-ref a 2))
+(define (set-annotation-stripped! a)
+  (struct-set! a 2 #t))
+
+(define (annotate e)
+  (cond ((list? e)
+         (make-annotation (map annotate e) (source-properties e) #f))
+        ((pair? e)
+         (make-annotation (cons (annotate (car e)) (annotate (cdr e)))
+                          (source-properties e) #f))
+        (else e)))
+                          
+