Class Builder

source code

Base class for states in the parser (called Builder rather than State to avoid confusion with the parser state).

The parser can be though of as a state machine, implemented via a separate loop (parse()) that repeatedly calls .append_character() on the current state, using whatever is returned as the next state.

The graph is assembled within the states, which either assemble locally or extend the state in a "parent" state (so states may reference parent states, but the evaluation process remains just a single level deep).

It is also possible for one state to delegate to the append_character method of another state (escapes are handled in this way, for example).

After all characters have been parsed, None is used as a final character to flush any state that is waiting for lookahead.