From ea1ef4c6ad6788bafe232f91d9a1bf03d48e4ff3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juan=20Manuel=20Tom=C3=A1s?= <jtomas1815@gmail.com>
Date: Sun, 30 Oct 2022 17:56:01 -0300
Subject: Add a number parser

Most of the spec regarding numbers is covered but currently
numbers can have leading 0's and + sign.
---
 json.asd     |  2 +-
 json.lisp    | 21 +++++++++++++++++++++
 package.lisp |  2 +-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/json.asd b/json.asd
index 598f9c5..19479bb 100644
--- a/json.asd
+++ b/json.asd
@@ -1,6 +1,6 @@
 (asdf:defsystem #:json
   :serial t
-  :depends-on ()
+  :depends-on (#:monparser)
   :components
   ((:file "package")
    (:file "json")))
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))))
diff --git a/package.lisp b/package.lisp
index df3e37c..609b6b4 100644
--- a/package.lisp
+++ b/package.lisp
@@ -1,2 +1,2 @@
 (defpackage #:json
-  (:use #:cl))
+  (:use #:cl #:parser))
-- 
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