modularize sex

Also rename macros to sex-macros, module-system to sex-modules for
clarity, uniformity, and to avoid name clashes with Chicken's
units/modules named "macros" and "modules"

reader.scm

@@ -0,0 +1,62 @@
+(import
+  scheme
+  (chicken base)
+  (chicken io)
+  (chicken pathname)
+  (chicken port)
+  (chicken read-syntax)
+  (chicken string)
+  (chicken syntax)
+  brev-separate
+  fmt)
+
+(import-syntax utils)
+
+(define (read-forms acc)
+  (let ((r (read-with-source-info (current-input-port))))
+    (if (eof-object? r) (reverse acc)
+        (read-forms (cons r acc)))))
+
+(define (read-from-file file)
+  (with-directory file
+                  (with-input-from-file (pathname-strip-directory file)
+                    (fn (read-forms (list))))))
+
+(define (read-bracket port)
+  (let loop ((c (read-char port))
+             (str (string)))
+    (cond ((char=? c #\])
+           (cons '¤
+                 (with-input-from-string str
+                   (fn (port-map identity read)))))
+          ((char=? c #\[)
+           (loop port (conc )))
+          (else
+           (loop (read-char port)
+                 (conc str c))))))
+
+(define open-bracket-counter (make-parameter 0))
+
+(define (read-raw-forms input-source)
+  (let ((bracket-end (gensym)))
+    (set-read-syntax!
+     #\]
+     (lambda (port)
+       (when (= 0 (open-bracket-counter))
+         (error "Unmatched closing bracket"))
+       (open-bracket-counter (- (open-bracket-counter) 1))
+       bracket-end))
+
+    (set-read-syntax!
+     #\[
+     (lambda (port)
+       (open-bracket-counter (+ (open-bracket-counter) 1))
+       (let loop ((r (read port))
+                  (acc (list)))
+         (if (eq? r bracket-end)
+             (cons '¤ (reverse acc))
+             (loop (read port)
+                   (cons r acc)))))))
+  (if (eq? input-source 'stdin)
+      (read-forms (list))
+      (read-from-file input-source)))