Fix gc bug and add condition classes

src/list.c

@@ -1,5 +1,7 @@
 #include "list.h"
 
+#include "function.h"
+
 intptr_t list_length(LispVal *list) {
     assert(LISTP(list));
     LispVal *tortise = list;
@@ -61,6 +63,25 @@ DEFUN(list, "list", (LispVal * args), "(&rest args)", "") {
     return args;
 }
 
+DEFUN(member, "member", (LispVal * elt, LispVal *list, LispVal *pred),
+      "(elt list &optional pred)", "") {
+    if (NILP(pred) || pred == Qeq) {
+        // fast case
+        DOTAILS(rest, list) {
+            if (elt == XCAR(rest)) {
+                return rest;
+            }
+        }
+    } else {
+        DOTAILS(rest, list) {
+            if (CALL(pred, elt, XCAR(rest))) {
+                return rest;
+            }
+        }
+    }
+    return Qnil;
+}
+
 DEFUN(plist_put, "plist-put", (LispVal * plist, LispVal *prop, LispVal *value),
       "(plist prop value)", "") {
     CHECK_LISTP(plist);