Improve flexibility

This will make it easier to run the parser in a multi-stage
setup without sacrificing the standalone setups.

Modified comp to extract the location of parsed things.

I expose the parts of the Input, Parsing and Failure objects
to customize error handling.

Parsing and Failure objects have a default printer now.

1 files changed, 23 insertions, 23 deletions

diff --git a/input.lisp b/input.lisp
index 8b031fd..a96888f 100644
--- a/input.lisp
+++ b/input.lisp
@@ -1,43 +1,43 @@
 (in-package #:input)
 
-(defstruct input
-  (cursor 0)
-  (file nil :read-only t)
-  (data nil :read-only t))
+(defclass input ()
+  ((cursor :initarg :cursor :accessor cursor :initform 0)
+   (file :initarg :file :reader file :initform nil)
+   (data :initarg :data :reader data :initform nil)))
 
-(defun has-data? (input &optional (window-size 1))
-  (<= (+ window-size (input-cursor input))
-      (length (input-data input))))
+(defun has-data? (input)
+  (< (cursor input) (length (data input))))
 
 (defun prefix? (target input)
-  (string= target (input-data input) :start2 (input-cursor input) :end2 (+ (input-cursor input) (length target))))
+  (string= target
+           (data input)
+           :start2 (cursor input)
+           :end2 (min (+ (cursor input) (length target))
+                      (length (data input)))))
 
 (defun peek (input)
-  (char (input-data input)
-        (input-cursor input)))
+  (char (data input)
+        (cursor input)))
 
 (defun advance (input &optional (amount 1))
-  (let ((new-input (copy-structure input)))
-    (incf (input-cursor new-input) amount)
-    new-input))
+  (make-instance 'input
+                 :data (data input)
+                 :file (file input)
+                 :cursor (1+ (cursor input))))
 
-(declaim (ftype (function (simple-string) (values input &optional)) from-string))
 (defun from-string (str)
-  (make-input :data str))
+  (make-instance 'input :data str))
 
-(declaim (ftype (function (simple-string) (values input &optional)) from-file))
 (defun from-file (filename)
-  (make-input :file filename :data (str:read-file filename)))
+  (make-instance 'input :file filename :data (str:read-file filename)))
 
-(defun generate-report (input message)
+(defun line-and-column (input)
   (let ((line 1) (column 1))
-    (dotimes (i (input-cursor input))
-      (let ((c (char (input-data input) i)))
+    (dotimes (i (cursor input))
+      (let ((c (char (data input) i)))
         (case c
           (#\Newline
            (incf line)
            (setf column 1))
           (t (incf column)))))
-    (if (input-file input)
-      (format nil "~a:~a:~a: ~a" (input-file input) line column message)
-      (format nil "~a:~a: ~a" line column message))))
+    (values line column)))