Error out on parser failure

3 files changed, 17 insertions, 1 deletions

diff --git a/input.lisp b/input.lisp
index e28e73a..100baa5 100644
--- a/input.lisp
+++ b/input.lisp
@@ -18,3 +18,14 @@
 
 (defun cursor-distance (input1 input2)
   (- (input-cursor input1) (input-cursor input2)))
+
+(defun line-and-column (input)
+  (let ((line 1) (column 1))
+    (dotimes (i (input-cursor input))
+      (let ((c (char (input-data input) i)))
+        (case c
+          (#\Newline
+           (incf line)
+           (setf column 1))
+          (t (incf column)))))
+    (values line column)))
diff --git a/main.lisp b/main.lisp
index 6357cc4..0d890a0 100644
--- a/main.lisp
+++ b/main.lisp
@@ -8,4 +8,8 @@
     (if (parsing-p result)
       (let ((finished? (not (has-data? (parsing-left result)))))
         (values (parsing-tree result) finished?))
-      result)))
+      (error (format nil "~a" result)))))
+
+(defmethod print-object ((obj failure) stream)
+  (multiple-value-bind (line column) (line-and-column (failure-place obj))
+    (format stream "~a:~a: ~a" line column (failure-message obj))))
diff --git a/package.lisp b/package.lisp
index c59f997..62846f2 100644
--- a/package.lisp
+++ b/package.lisp
@@ -5,6 +5,7 @@
            #:failure-message
            #:input-cursor
            #:input-data
+           #:line-and-column 
            #:comp
            #:one-of
            #:unit