From 7486de914e5a797017129f432490b8c235364659 Mon Sep 17 00:00:00 2001
From: Tom Smeding <tom.smeding@gmail.com>
Date: Thu, 21 Nov 2019 23:24:15 +0100
Subject: WIP lisp parser in lisp

---
 tests/lispparser.lisp | 61 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 61 insertions(+)
 create mode 100644 tests/lispparser.lisp

diff --git a/tests/lispparser.lisp b/tests/lispparser.lisp
new file mode 100644
index 0000000..4579b93
--- /dev/null
+++ b/tests/lispparser.lisp
@@ -0,0 +1,61 @@
+#include "stdlib.lisp"
+
+(define str-elem (ch str)
+    (if (= str "") 0
+        (if (= ch (substr 0 1 str)) 1
+            (str-elem ch (substr 1 -1 str)))))
+
+(define isspace? (ch)
+    (str-elem ch " \n\t\r"))
+
+(define isdigit? (ch)
+    (let ((n (ord ch))) (and (<= 48 n) (<= 57 n))))
+
+(define lowercase? (ch)
+    (let ((n (ord ch))) (and (<= 97 n) (<= n 122))))
+
+(define uppercase? (ch)
+    (let ((n (ord ch))) (and (<= 65 n) (<= n 90))))
+
+(define iswordchar? (ch)
+    (or (str-elem ch "-_?")
+        (or (lowercase? ch) (uppercase? ch))))
+
+(define isrestwordchar? (ch)
+    (or (iswordchar? ch) (isdigit? ch)))
+
+(define parse-int (str)
+    (let ((helper (lambdarec rec (str n)
+                        (let ((ch (substr 0 1 str))
+                              (rest (substr 1 -1 str)))
+                            (if (isdigit? ch)
+                                (rec rest (+ (* 10 n) (- (ord ch) 48)))
+                                n)))))
+        (helper str 0)))
+
+(define next-token (str)
+    (let ((ch (substr 0 1 str))
+          (rest (substr 1 -1 str)))
+        (cond
+            (= ch "")
+                '()
+            (isspace? ch)
+                (next-token rest)
+            (= ch ";")
+                (next-token (drop-while (lambda (c) (not (= c "\n"))) rest))
+            (= ch "(")
+                (list "(" rest)
+            (= ch ")")
+                (list ")" rest)
+            (iswordchar? ch)
+                (let ((restword (take-while isrestwordchar? rest)))
+                    (list (concat ch restword) (substr (length restword) -1 rest)))
+            (isdigit? ch)
+                (let ((word (concat ch (take-while isdigit? rest))))
+                    (list (parse-int word) (substr (length word) -1 str)))
+            (do
+                (print (concat "Invalid token: " ch))
+                (exit)))))
+
+; (define parse-sexpr (tokens)
+;     ...)
-- 
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