Method putback

code_snippets/Chapter07/chapter.7.7-problematic.cpp:100–105

The putback() member function puts its argument back into the Token_stream's buffer:

// The putback() member function puts its argument back into the Token_stream's buffer:
void Token_stream::putback(Token t)
{
    if (full) error("putback() into a full buffer");
    buffer = t;       // copy t to buffer
    full = true;      // buffer is now full
}

//------------------------------------------------------------------------------