diff --git a/src/lisp/lib/std.c b/src/lisp/lib/std.c
index 7bed8de..8175940 100644
--- a/src/lisp/lib/std.c
+++ b/src/lisp/lib/std.c
@@ -9,6 +9,30 @@
 	return (((a >> 2) + (b >> 2)) << 2) | INT_TAG;
 }
 
+value_t l_minus (value_t a, value_t b)
+{
+	if ( !integerp (a) || !integerp (b) )
+		return nil;
+
+	return (((a >> 2) - (b >> 2)) << 2) | INT_TAG;
+}
+
+value_t l_times (value_t a, value_t b)
+{
+	if ( !integerp (a) || !integerp (b) )
+		return nil;
+
+	return (((a >> 2) * (b >> 2)) << 2) | INT_TAG;
+}
+
+value_t l_divide (value_t a, value_t b)
+{
+	if ( !integerp (a) || !integerp (b) )
+		return nil;
+
+	return (((a >> 2) / (b >> 2)) << 2) | INT_TAG;
+}
+
 void add_function (struct environment *env, char *name, void *func, int nargs)
 {
 	struct function *last,
@@ -26,4 +50,7 @@
 void load_std (struct environment *env)
 {
 	add_function (env, "+", l_plus, 2);
+	add_function (env, "-", l_minus, 2);
+	add_function (env, "*", l_times, 2);
+	add_function (env, "/", l_divide, 2);
 }
diff --git a/src/lisp/lisp b/src/lisp/lisp
index 2421bd3..492c456 100755
--- a/src/lisp/lisp
+++ b/src/lisp/lisp
Binary files differ