1 files changed, 40 insertions, 0 deletions
diff --git a/python/sexpr.py b/python/sexpr.py
new file mode 100644
index 0000000..61bb09c
--- /dev/null
+++ b/python/sexpr.py
@@ -0,0 +1,40 @@
+
+def tokenize(s, sep="()", ws=" \t\n"):
+    L = []
+    food = 0
+    for i, c in enumerate(s):
+        if c in sep or c in ws:
+            if food > 0:
+                L.append(s[i-food:i])
+            if c in sep:
+                L.append(c)
+            food = 0
+        elif i+1 == len(s):
+            L.append(s[i-food:])
+        else:
+            food += 1
+    return L
+
+def _parse_tokens(tokens, depth=0):
+    L = []
+    i = 0
+    while i < len(tokens):
+        el = tokens[i]
+        if el == '(':
+            expr, skip = _parse_tokens(tokens[i+1:], depth+1)
+            L.append(expr)
+            i += skip + 1
+        elif el == ')':
+            assert depth > 0, "Missing open bracket..."
+            return L, i+1
+        else:
+            L.append(el)
+            i += 1
+    assert depth == 0, "Missing close bracket..."
+    return L, i
+
+def parse(s):
+    tokens = tokenize(s)
+    expr, size = _parse_tokens(tokens)
+    return expr[0]
+