Add a number parser

Most of the spec regarding numbers is covered but currently
numbers can have leading 0's and + sign.

1 files changed, 21 insertions, 0 deletions

diff --git a/json.lisp b/json.lisp
index b9ea796..2bc94db 100644
--- a/json.lisp
+++ b/json.lisp
@@ -1 +1,22 @@
 (in-package #:json)
+
+(defparameter number-parser
+  (let ((signed-digits
+          (comp ((sign (zero-or-one (unit (lambda (x) (or (char= x #\-)
+                                                          (char= x #\+))))))
+                 (natural (one-or-more (unit #'digit-char-p))))
+            (cons sign natural))))
+    (comp ((base (any signed-digits
+                      (fail "Malformed number.")))
+           (dot (zero-or-one (unit (lambda (x) (char= x #\.)))))
+           (fraction (if dot
+                       (any (one-or-more (unit #'digit-char-p))
+                            (fail "Malformed fractional part."))
+                       (new nil)))
+           (e (zero-or-one (unit (lambda (x) (or (char= x #\e)
+                                                 (char= x #\E))))))
+           (exponent (if e
+                       (any signed-digits
+                            (fail "Malformed exponent part."))
+                       (new nil))))
+      (list 'number base fraction exponent))))