Method scrape

openvdb_cmd/vdb_tool/include/Parser.h:173–176

        mData.erase(mData.end()-2);
    }
    void scrape() {// ... x -- x
        if (mData.empty()) throw std::invalid_argument("Stack::scrape: empty stack");
        mData.erase(mData.begin(), mData.end()-1);
    }
    void clear() {mData.clear();}
    void over() {// y x -- y x y
        if (mData.size()<2) throw std::invalid_argument("Stack::over: size<2");