Add basic lexenv support

src/list.c

@@ -60,3 +60,26 @@ DEFUN(listp, "listp", (LispVal * obj), "(obj)", "") {
 DEFUN(list, "list", (LispVal * args), "(&rest args)", "") {
     return args;
 }
+
+DEFUN(plist_put, "plist-put", (LispVal * plist, LispVal *prop, LispVal *value),
+      "(plist prop value)", "") {
+    CHECK_LISTP(plist);
+    DOTAILS(rest, plist) {
+        if (EQ(XCAR(rest), prop)) {
+            RPLACA(XCDR(rest), value);
+            return plist;
+        }
+    }
+    return CONS(prop, CONS(value, plist));
+}
+
+DEFUN(plist_get, "plist-get", (LispVal * plist, LispVal *prop, LispVal *def),
+      "(plist prop &optional default)", "") {
+    CHECK_LISTP(plist);
+    DOTAILS(rest, plist) {
+        if (EQ(XCAR(rest), prop)) {
+            return SECOND(rest);
+        }
+    }
+    return def;
+}