Defining the socket construct.

§1. This is a pseudo-construct: it looks like an instruction in textual Inter syntax, but specifies something else, and does not result in an inter_tree_node.

void SocketInstruction::define_construct?Usage of SocketInstruction::define_construct:
Inter Constructs - §15(void) {
    inter_construct *IC = InterInstruction::create_construct(SOCKET_IST, I"socket");
    InterInstruction::specify_syntax(IC, I"socket IDENTIFIER TOKENS");
    METHOD_ADD(IC, CONSTRUCT_READ_MTID, SocketInstruction::read);
    METHOD_ADD(IC, CONSTRUCT_VERIFY_MTID, SocketInstruction::verify);
    InterInstruction::allow_in_depth_range(IC, 0, 1);
    InterInstruction::permit(IC, INSIDE_PLAIN_PACKAGE_ICUP);
}

void SocketInstruction::verify(inter_construct *IC, inter_tree_node *P,
    inter_package *owner, inter_error_message **E) {
    *E = Inode::error(P, I"SOCKET_IST structures cannot exist", NULL);
}

§2. What it does is to specify a symbol which is a socket in the current tree: this results in an entry in the symbols table for the current package (which will always be /main/connectors, in fact) but not an instruction.

For how these are printed back, see PlugInstruction::write_declaration, which handles both plugs and sockets.

void SocketInstruction::read?Usage of SocketInstruction::read:
§1(inter_construct *IC, inter_bookmark *IBM, inter_line_parse *ilp,
    inter_error_location *eloc, inter_error_message **E) {
    text_stream *symbol_text = ilp->mr.exp[0];
    text_stream *equate_text = ilp->mr.exp[1];

    inter_tree *I = InterBookmark::tree(IBM);
    inter_symbols_table *T = InterBookmark::scope(IBM);
    inter_symbol *socket_s = TextualInter::new_symbol(eloc, T, symbol_text, E);
    if (*E) return;

    text_stream *equate_name = NULL;
    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, equate_text, U"~~> \"(%C+)\"")) {
        *E = InterErrors::plain(I"a socket cannot wire to a name", eloc);
        return;
    } else if (Regexp::match(&mr, equate_text, U"~~> (%C+)")) {
        equate_name = mr.exp[0];
    } else {
        Regexp::dispose_of(&mr);
        *E = InterErrors::plain(I"bad socket syntax", eloc); return;
    }

    inter_symbol *eq = InterSymbolsTable::URL_to_symbol(I, equate_name);
    if (eq == NULL) {
        InterSymbol::make_socket(socket_s);
        Wiring::wire_to_name(socket_s, equate_name);
    } else {
        Wiring::make_socket_to(socket_s, eq);
    }
    Regexp::dispose_of(&mr);
}