Add better reporting and new features

Units report expected results on end of input.
Opposite parser helps with the complexity explosion
on unit parsers.
Input and error printing has context.

1 files changed, 12 insertions, 5 deletions

diff --git a/input.lisp b/input.lisp
index 55a72cb..5d6a162 100644
--- a/input.lisp
+++ b/input.lisp
@@ -28,10 +28,17 @@
     (values line column)))
 
 (defmethod print-object ((obj parser-input) stream)
-  (let ((context-length 10))
+  (let ((context-length 20))
     (let ((begin (max (- (input-cursor obj) context-length) 0))
           (end (min (+ (input-cursor obj) context-length) (length (input-data obj)))))
-      (format stream "...~a~a~a..."
-              (substitute #\¶ #\Newline (subseq (input-data obj) begin (input-cursor obj)))
-              (substitute #\¶ #\Newline (subseq (input-data obj) (input-cursor obj) (1+ (input-cursor obj))))
-              (substitute #\¶ #\Newline (subseq (input-data obj) (1+ (input-cursor obj)) end))))))
+      (when (< 0 begin)
+        (format stream "..."))
+      (format stream "~a"
+              (substitute #\↲ #\Newline (subseq (input-data obj) begin (input-cursor obj))))
+      (if (< (input-cursor obj) (length (input-data obj)))
+        (format stream "~a~a"
+                (substitute #\↲ #\Newline (subseq (input-data obj) (input-cursor obj) (1+ (input-cursor obj))))
+                (substitute #\↲ #\Newline (subseq (input-data obj) (1+ (input-cursor obj)) end)))
+        (format stream "¬"))
+        (when (< end (length (input-data obj)))
+          (format stream "...")))))