To parse sentences like "The plural of woman is women".

§1. Stocking the plurals dictionary. The user gives us plurals with special sentences, whose subject is like so: 

    <plural-sentence-subject> ::=
        <article> plural of <nounphrase-articled> |				==> TRUE; *XP = RP[2]
        plural of <nounphrase-articled>							==> TRUE; *XP = RP[1]

§2. We take immediate action on parsing the sentence, and after that ignore it as having been dealt with.

Note that we are entirely allowed to register a new plural for a phrase which already has a plural in the dictionary, which is why we do not trouble to search the existing dictionary here. 

    int Plurals::plural_SMF(int task, parse_node *V, wording *NPs) {
        wording SW = (NPs)?(NPs[0]):EMPTY_WORDING;
        wording OW = (NPs)?(NPs[1]):EMPTY_WORDING;
        switch (task) {     "The plural of woman is women."
            case ACCEPT_SMFT:
                FSW = SW; FOW = OW;
                if (<plural-sentence-subject>(SW)) {
                    ParseTree::annotate_int(V, verb_id_ANNOT, SPECIAL_MEANING_VB);
                    V->next = <<rp>>;
                    <nounphrase>(OW);
                    V->next->next = <<rp>>;
                    wording S = ParseTree::get_text(V->next);
                    wording P = ParseTree::get_text(V->next->next);
                    <Forbid plural declarations containing quoted text 2.1>;
                    if (Assertions::Creator::vet_name_for_noun(P) == FALSE) return TRUE;
                    Pluralisation::register(S, P, English_language);
                    return TRUE;
                }
                break;
        }
        return FALSE;
    }

The function Plurals::plural_SMF is used in 6/nv (§16).

§2.1. In general names of things which we need plurals for cannot contain quoted text anyway, so the following problem messages are not too gratuitous.

<Forbid plural declarations containing quoted text 2.1> = 

        LOOP_THROUGH_WORDING(i, S)
            if (Vocabulary::test_flags(i, TEXT_MC+TEXTWITHSUBS_MC)) {
                Problems::Issue::sentence_problem(_p_(PM_PluralOfQuoted),
                    "declares a plural for a phrase containing quoted text",
                    "which is forbidden. Sentences like this are supposed to "
                    "declare plurals without quotation marks: for instance, "
                    "'The plural of attorney general is attorneys general.'");
                return TRUE;
            }
        LOOP_THROUGH_WORDING(i, P)
            if (Vocabulary::test_flags(i, TEXT_MC+TEXTWITHSUBS_MC)) {
                Problems::Issue::sentence_problem(_p_(PM_PluralIsQuoted),
                    "declares a plural for a phrase using quoted text",
                    "which is forbidden. Sentences like this are supposed to "
                    "declare plurals without quotation marks: for instance, "
                    "'The plural of procurator fiscal is procurators fiscal.'");
                return TRUE;
            }

This code is used in §2.