Added block comment support

docs/Scheme-Language-Compliance.md

@@ -4,7 +4,7 @@ This is the status of Scheme programming language features implemented from the
 
 Section | Status | Comments
 ------- | ------ | ---------
-2.2 Whitespace and comments | Partial | No datum or block comments
+2.2 Whitespace and comments | Partial | No datum comments
 2.3 Other notations | Yes | 
 2.4 Datum labels | No |
 3.1 Variables, syntactic keywords, and regions | Yes |

scheme/read.sld

@@ -302,6 +302,10 @@
             (in-port:set-cnum! ptbl
                 (+ 1 (in-port:get-cnum ptbl)))
             (cond
+              ;; Block comments
+              ((eq? #\| next-c)
+               (read-block-comment fp ptbl)
+               (parse fp '() toks all? #f parens ptbl))
               ;; Booleans
               ;; Do not use add-tok below, no need to quote a bool
               ((eq? #\t next-c) 
@@ -473,6 +477,21 @@
       (in-port:read-buf! ptbl) ;; Already buffered
       (read-char fp)))
 
+;; Read chars in the middle of a block comment
+(define (read-block-comment fp ptbl)
+  (let ((c (get-next-char fp ptbl)))
+    (cond
+      ((eq? #\| c) (read-block-terminator fp ptbl))
+      (else (read-block-comment fp ptbl)))))
+
+;; Read (possibly) the end of a block comment
+(define (read-block-terminator fp ptbl)
+  (let ((c (get-next-char fp ptbl)))
+    (cond
+      ((eq? #\# c) #t)
+      ((eq? #\| c) (read-block-terminator fp ptbl))
+      (else (read-block-comment fp ptbl)))))
+
 (define (parse-number fp toks all? parens ptbl base tok->num)
 ;  (parse-number-rec base fp '() ptbl))
   (let ((num (parse-number-rec base fp '() ptbl)))