Fix some bugs

src/list.c

@@ -53,6 +53,20 @@ DEFUN(cdr, "cdr", (LispVal * list), "(list)", "") {
     return NILP(list) ? Qnil : XCDR(list);
 }
 
+DEFUN(rplaca, "rplaca", (LispVal * cons, LispVal *newcar), "(cons newcar)",
+      "") {
+    CHECK_TYPE(cons, TYPE_CONS);
+    RPLACA(cons, newcar);
+    return newcar;
+}
+
+DEFUN(rplacd, "rplacd", (LispVal * cons, LispVal *newcdr), "(cons newcdr)",
+      "") {
+    CHECK_TYPE(cons, TYPE_CONS);
+    RPLACD(cons, newcdr);
+    return newcdr;
+}
+
 DEFUN(length_eq, "length=", (LispVal * list, LispVal *length), "(list length)",
       "Return non-nil if LIST's length is LENGTH.") {
     CHECK_LISTP(list);