This section provides a simple API for storing and retrieving lexicon entries.

§1. The user creates new lexicon entries with:

excerpt_meaning *Lexicon::register(
    unsigned int meaning_code, wording W, general_pointer data) {
    if (Wordings::empty(W)) internal_error("tried to register empty excerpt meaning");
    return ExcerptMeanings::register(meaning_code, W, data);
}

§2. excerpt_meaning objects are intended to be fairly opaque, but the user can call this to extract their attached data:

general_pointer Lexicon::get_data?Usage of Lexicon::get_data:
Parse Excerpts - §7(excerpt_meaning *em) {
    return em->data;
}

§3. Entries can be retrieved either the regular way, or in "maximal mode", which tries to parse a maximal-length initial portion of W rather than necessarily the whole thing. For example, that mode might peel off the adjective "fixed in place" from wording W which was "fixed in place door". This is very much the exception: we almost always want to match the whole of W.

It might seem symmetrical that the return value should be an excerpt_meaning. But that wouldn't enable us to return multiple results in the (frequent) case of ambiguity. Instead, we need to return a list of possibilities, and we do that by returning fragment of syntax tree material, using the infrastructure from syntax. This will be a list of nodes joined by ->next_alternative limks.

This list of nodes is disposable — even if it is a copy of something from the syntax tree, it is never the only copy. It can freely be ignored or changed. A return value of NULL means there were no results at all.

• ● If a meaning was registered in such a way that its data actually was a node from the syntax tree, then the result is a copy of that node.
• ● If not then the result is a node with the meaning code as its node type, and the excerpt meaning can be recovered from it using Node::get_meaning.

parse_node *Lexicon::retrieve(unsigned int mc_bitmap, wording W) {
    return FromLexicon::parse(mc_bitmap, W);
}

int lexicon_in_maximal_mode = FALSE;
parse_node *Lexicon::retrieve_longest_initial_segment(unsigned int mc_bitmap,
    wording W) {
    int s = lexicon_in_maximal_mode;
    lexicon_in_maximal_mode = TRUE;
    parse_node *p = FromLexicon::parse(mc_bitmap, W);
    lexicon_in_maximal_mode = s;
    return p;
}

§4. As a bonus, since the lexicon uses quite a convenient hash-coding system for excerpts, the following is available for anyone wanting to take advantage:

int Lexicon::wording_hash(wording W) {
    return ExcerptMeanings::hash_code(W);
}