To manage and compile tables, which are two-dimensional arrays with associative look-up facilities provided at run-time.

§1. This is how a table is stored. Note that the limit on columns per table must not rise to 100 or beyond because that would break the system of table column ID numbers: see Tables (in runtime). 

define MAX_COLUMNS_PER_TABLE 99

typedef struct table {
    struct wording table_no_text;  the table number (if any)
    struct wording table_name_text;  the table name (if any)
    struct table_contribution *table_created_at;  where created in source
    struct parse_node *headline_fragment;  a pseudo-sentence formed by the heading line
    int blank_rows;  number of entirely blank rows to be appended (may be 0)
    struct wording blank_rows_for_each_text;  add one blank for each instance
    struct wording blank_rows_text;  text of blank rows specification
    int fill_in_blanks;  if set, fill any blank entries with default values
    int first_column_by_definition;  if set, first column defines new value names
    struct kind *kind_defined_in_this_table;  ...of this kind
    int contains_property_values_at_run_time;
    struct parse_node *where_used_to_define;
    int preserve_row_order_at_run_time;  if set, don't sort this table
    struct table *amendment_of;  if amendment of earlier table
    int has_been_amended;  if there exists an amendment of this
    int approximate_array_space_needed;  at run-time, in words
    int disable_block_constant_correction;  if set, don't translate block constant entries

    int no_columns;  must be at least 1
    struct table_column_usage columns[MAX_COLUMNS_PER_TABLE];

    struct table_compilation_data compilation_data;
    CLASS_DEFINITION
} table;

§2. For indexing purposes only: 

typedef struct table_contribution {
    struct parse_node *source_table;
    struct table_contribution *next;
} table_contribution;

§3. These are convenient during parsing. 

parse_node *table_cell_node = NULL;
int table_cell_row = -1;
int table_cell_col = -1;
table *table_being_examined = NULL;

§4. Traversing for tables. Tables of data are created in two passes through the source text: the first finds their names and registers them with the parser, while the second (much later) works out their columns and contents. At some point we also try to find ambiguity problems which might bite us later on.

Here is that later one. By this point all of the constant values in Inform exist, and so do all of the kinds, so we can now make sense of the kinds of the columns and of what's in them; and we can check that this is all consistent. This is called "stocking", and it comes in three phases: see below. 

void Tables::traverse_to_stock(void) {
    for (int phase = 1; phase <= 3; phase++) {
        table *t;
        LOOP_OVER(t, table) {
            current_sentence = t->table_created_at->source_table;
            Tables::stock_table(t, phase);
        }
    }
}

§5. Last and least: a traverse existing just to issue a problem message in a case which Inform can often cope with, but which the experience of users suggests is never a good idea. 

void Tables::check_tables_for_kind_clashes(void) {
    table *t;
    LOOP_OVER(t, table) {
        if ((Wordings::nonempty(t->table_name_text)) &&
            (<k-kind-articled>(t->table_name_text)) &&
            (Kinds::Behaviour::is_subkind_of_object(<<rp>>))) {
            Problems::quote_table(1, t);
            Problems::quote_wording(2, t->table_name_text);
            StandardProblems::handmade_problem(Task::syntax_tree(),
                _p_(PM_TableCoincidesWithKind));
            Problems::issue_problem_segment(
                "The name %1 will have to be disallowed because '%2' is also the "
                "name of a kind, or of the plural of a kind. (For instance, writing "
                "'Table of Rooms' is disallowed - it could lead to great confusion.)");
            Problems::issue_problem_end();
        }
    }
}

§6. Table basics. The following makes a blank structure for a table, but it isn't valid until some of these fields have been properly filled in. 

table *Tables::new_table_structure(parse_node *PN, wording W) {
    table *t = CREATE(table);
    t->table_no_text = EMPTY_WORDING;
    t->table_name_text = EMPTY_WORDING;
    t->headline_fragment = Diagrams::new_UNPARSED_NOUN(W);
    t->blank_rows = 0;
    t->blank_rows_text = EMPTY_WORDING;
    t->blank_rows_for_each_text = EMPTY_WORDING;
    t->fill_in_blanks = FALSE;
    t->first_column_by_definition = FALSE;
    t->kind_defined_in_this_table = NULL;
    t->where_used_to_define = NULL;
    t->contains_property_values_at_run_time = FALSE;
    t->preserve_row_order_at_run_time = FALSE;
    t->amendment_of = NULL;
    t->has_been_amended = FALSE;
    t->approximate_array_space_needed = 0;
    t->disable_block_constant_correction = FALSE;
    t->no_columns = 0;
    t->table_created_at = NULL;
    t->compilation_data = RTTables::new_table(PN, t, W);
    Tables::add_table_contribution(t, current_sentence);
    return t;
}

§7. A little linked list of chunks of source contributing to the table: 

void Tables::add_table_contribution(table *t, parse_node *src) {
    table_contribution *tc = CREATE(table_contribution);
    tc->source_table = src;
    tc->next = NULL;
    table_contribution *ltc = t->table_created_at;
    while ((ltc) && (ltc->next)) ltc = ltc->next;
    if (ltc) ltc->next = tc; else t->table_created_at = tc;
}

§8. Logging: 

void Tables::log(table *t) {
    LOG("{%n}", RTTables::identifier(t));
}

§9. Dimensions: 

int Tables::get_no_columns(table *t) {
    return t->no_columns;
}

int Tables::get_no_rows(table *t) {
    parse_node *PN; int c=0;
    for (PN=t->columns[0].entries->down; PN; PN=PN->next) c++;
    c += t->blank_rows;
    return c;
}

parse_node *Tables::cells_in_ith_column(table *t, int i) {
    if (t == NULL) internal_error("no such table");
    if ((i<0) || (i>=t->no_columns)) internal_error("column out of range");
    return t->columns[i].entries->down;
}

§10. Miscellaneous services: 

int Tables::expand_block_constants(table *t) {
    if (t->amendment_of) return FALSE;
    if (t->disable_block_constant_correction) return FALSE;
    return TRUE;
}

kind *Tables::kind_of_ith_column(table *t, int i) {
    if ((i<0) || (i>=t->no_columns))
        internal_error("tcdt for column out of range");
    return Tables::Columns::get_kind(t->columns[i].column_identity);
}

§11. Oddball forms of naming: 

parse_node *Tables::get_headline(table *t) {
    return t->headline_fragment;
}

§12. The author can demand with a "translates as" sentence that a given table should have an identifier given to it which is accessible to Inter: 

void Tables::translates(wording W, parse_node *p2) {
    if (<s-constant-value>(W)) {
        table *T = Rvalues::to_table(<<rp>>);
        if (T) {
            RTTables::translate(T, Node::get_text(p2));
            return;
        }
    }
    LOG("Tried %W\n", W);
    StandardProblems::sentence_problem(Task::syntax_tree(),
        _p_(PM_TranslatesNonTable),
        "this is not the name of a table",
        "so cannot be translated.");
}

§13. Table creation. Tables can be new, when they appear in the source, or can be related to already-existing ones with the same name: 

define TABLE_IS_NEW 1
define TABLE_IS_CONTINUED 2
define TABLE_IS_AMENDED 3
define TABLE_IS_REPLACED 4

§14. Their headers can have three forms: 

define TABLE_HAS_ONLY_NUMBER 1
define TABLE_HAS_ONLY_NAME 2
define TABLE_HAS_NUMBER_AND_NAME 3

§15. The source text declaration of tables is not easy to parse. Tabs are significantly different from spaces or new-lines, for instance — so the ordinary rules about white space are suspended. Tabs divide entries in a row; new-lines divide rows in a paragraph; and the table is terminated by a paragraph break.

If a table is declared as

Table 12 - Chemical Elements

then it can be referred to elsewhere in the source either as "Table 12" or as "Table of Chemical Elements", so both excerpts are registered as meaningful. But it is legal to declare a table with only one of the two forms in any case. 

<table-header> ::=
    <table-new-name> ( continued ) |  ==> { TABLE_IS_CONTINUED, -, <<nameforms>> = R[1] }
    <table-new-name> ( amended ) |    ==> { TABLE_IS_AMENDED, -, <<nameforms>> = R[1] }
    <table-new-name> ( replaced ) |   ==> { TABLE_IS_REPLACED, -, <<nameforms>> = R[1] }
    <table-new-name>                  ==> { TABLE_IS_NEW, -, <<nameforms>> = R[1] }

<table-new-name> ::=
    table ... - ... |                 ==> { TABLE_HAS_NUMBER_AND_NAME, - }
    table ### |                       ==> { TABLE_HAS_ONLY_NUMBER, - }
    table of ... |                    ==> { TABLE_HAS_ONLY_NAME, - }
    table ...                         ==> Issue PM_TableMisnamed problem15.1

§15.1. Issue PM_TableMisnamed problem15.1 = 

    StandardProblems::sentence_problem(Task::syntax_tree(), _p_(PM_TableMisnamed),
        "this isn't allowed as the name of a Table",
        "since a table is required either to have a number, or to be a table 'of' "
        "something (or both). For example: 'Table 5', 'Table of Blue Meanies', and "
        "'Table 2 - Submarine Hues' are all allowed, but 'Table concerning "
        "Pepperland' is not.");
    ==> { TABLE_HAS_ONLY_NAME, - };

§16. The following is then used to register table names as constants. The idea is that "Table 12 - Chemical Elements" will be registered both as Table 12 and as Table of Chemical Elements. 

<table-names-construction> ::=
    table ... |
    table of ...

§17. Optionally, tables can have a footer line specifying additional entirely blank rows. In (b), the ... is eventually required to be a kind, but this happens later on, since the bare bones of tables are parsed very early in Inform's run, when kinds haven't yet been created. 

<table-footer> ::=
    *** with <cardinal-number> blank row/rows |  ==> { R[1], -, <<each>> = FALSE }
    *** with ... blank row/rows |                ==> { 0, -, <<each>> = NOT_APPLICABLE }
    *** with blank row/rows for each/every ...   ==> { 0, -, <<each>> = TRUE }

§18. So, here goes. We first identify the top line of the table declaration (the "headline"), then set the current sentence to that, even though in parse tree terms it's only a fragment of a sentence: this makes problem messages about the headline much more readable. We extract the table's name, number and connection to other tables, and count its rows. In some cases, for example where we are continuing an existing table, we use the new table structure only temporarily: we transfer its rows to the existing table and then destroy the temporary one made here. 

void Tables::create_table(parse_node *PN) {
    wording W = Node::get_text(PN);
    int connection = TABLE_IS_NEW;  i.e., no connection with existing tables

    wording HW = Wordings::up_to(W, Wordings::last_word_of_formatted_text(W, FALSE));
    if (Wordings::length(HW) == 1) Reject this lexically malformed table declaration18.1;

    table *t = Tables::new_table_structure(PN, HW);
    current_sentence = t->headline_fragment;

    Parse the table's header for a name and/or number, and connection to other tables18.2;
    Require the table name not to tread on some other value18.3;

    table *existing_table_with_same_name = NULL;
    Find the first existing table with the same name, if any18.4;
    if (connection != TABLE_IS_NEW) Require the previous table to exist18.5
    else Require the previous table not to exist18.6;

    if (connection == TABLE_IS_NEW) {
        Register the names of the new table18.7;
        LOGIF(TABLES, "Created: $B\n", t);
    }

    Parse the table's footer for a number of blank rows18.8;
    int row_count = 0;
    Count out the rows and columns in the new table18.9;

    if (connection != TABLE_IS_NEW)
        Act on the connection, possibly destroying the temporary table just made18.10;
}

§18.1. Changes to the lexer mean that this shouldn't happen, but just in case:

Reject this lexically malformed table declaration18.1 = 

    StandardProblems::sentence_problem(Task::syntax_tree(), _p_(BelievedImpossible),
        "this table does not strictly speaking start a paragraph",
        "and I'm afraid we need to speak strictly here. Even a comment coming before "
        "the start of the table is too much.");
    return;

§18.2. Parse the table's header for a name and/or number, and connection to other tables18.2 = 

    LOGIF(TABLES, "Parsing table headline %W\n", HW);
    <table-header>(HW);
    connection = <<r>>;

    switch (<<nameforms>>) {
        case TABLE_HAS_ONLY_NUMBER:
            t->table_no_text = GET_RW(<table-new-name>, 1);
            break;
        case TABLE_HAS_ONLY_NAME:
            t->table_name_text = GET_RW(<table-new-name>, 1);
            break;
        case TABLE_HAS_NUMBER_AND_NAME:
            t->table_no_text = GET_RW(<table-new-name>, 1);
            t->table_name_text = GET_RW(<table-new-name>, 2);
            break;
    }

    if ((Wordings::length(t->table_no_text) > 24) ||
        (Wordings::length(t->table_name_text) > 24)) {
        if (Wordings::length(t->table_no_text) > 24)
            Problems::quote_wording_as_source(1, t->table_no_text);
        else
            Problems::quote_wording_as_source(1, t->table_name_text);
        StandardProblems::handmade_problem(Task::syntax_tree(), _p_(PM_TableNameTooLong));
        Problems::issue_problem_segment(
            "This table has been called %1, but that's just too much text. Tables "
            "really don't need names longer than 20 words.");
        Problems::issue_problem_end();
        DESTROY(t, table);
        return;
    }

§18.3. Practical experience showed that the following restriction was wise:

Require the table name not to tread on some other value18.3 = 

    if (<s-type-expression-or-value>(t->table_name_text)) {
        Problems::quote_wording_as_source(1, t->table_name_text);
        StandardProblems::handmade_problem(Task::syntax_tree(), _p_(PM_TableNameAmbiguous));
        Problems::issue_problem_segment(
            "The table name %1 will have to be disallowed as it is text which "
            "already has a meaning to Inform. For instance, creating the 'Table "
            "of Seven' would be disallowed because of the possible confusion "
            "with the number 'seven'.");
        Problems::issue_problem_end();
        DESTROY(t, table);
        return;
    }

§18.4. It's not as simple as it seems to decide when a new table headline refers back to a table which already exists — there are several ways we could play this. What we say is that if the new headline gives both name and number, then both must match; if it gives name only, that must match; if it gives number only, that must. Suppose that "Table 2 - Trees" already exists. Then: 

define TABLE_NAMES_MATCH(t1, t2)
    ((t1 != t2) && (Wordings::nonempty(t1->table_name_text)) &&
        (Wordings::nonempty(t2->table_name_text)) &&
        (Wordings::match(t2->table_name_text, t1->table_name_text)))
define TABLE_NUMBERS_MATCH(t1, t2)
    ((t1 != t2) && (Wordings::nonempty(t1->table_no_text)) &&
        (Wordings::nonempty(t2->table_no_text)) &&
        (Wordings::match(t2->table_no_text, t1->table_no_text)))

Find the first existing table with the same name, if any18.4 = 

    if ((Wordings::nonempty(t->table_name_text)) &&
        (Wordings::nonempty(t->table_no_text))) {
        table *t2;
        LOOP_OVER(t2, table)
            if ((TABLE_NAMES_MATCH(t2, t)) && (TABLE_NUMBERS_MATCH(t2, t)))
                existing_table_with_same_name = t2;
    } else if (Wordings::nonempty(t->table_name_text)) {
        table *t2;
        LOOP_OVER(t2, table)
            if (TABLE_NAMES_MATCH(t2, t)) {
                if ((Wordings::nonempty(t->table_no_text)) &&
                    (!(TABLE_NUMBERS_MATCH(t2, t))))
                    continue;
                existing_table_with_same_name = t2;
            }
    } else if (Wordings::nonempty(t->table_no_text)) {
        table *t2;
        LOOP_OVER(t2, table)
            if (TABLE_NUMBERS_MATCH(t2, t))
                existing_table_with_same_name = t2;
    }

§18.5. Require the previous table to exist18.5 = 

    if (existing_table_with_same_name == NULL) {
        Problems::quote_table(1, t);
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableNotContinuation));
        Problems::issue_problem_segment(
            "It looks as if %1 is meant to be related to an existing table, "
            "but I can't find one if it is. %P"
            "Perhaps you've put the new part before the original? The original "
            "has to be earlier in the source text.");
        Problems::issue_problem_end();
        DESTROY(t, table);
        return;
    }

§18.6. Require the previous table not to exist18.6 = 

    if (existing_table_with_same_name) {
        Problems::quote_table(1, t);
        Problems::quote_table(2, existing_table_with_same_name);
        Problems::quote_wording(3, HW);
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableNameDuplicate));
        Problems::issue_problem_segment(
            "I can't create %1 because its name overlaps with one that already "
            "exists: %2. %P"
            "It's possible to continue the existing one, if you just want to "
            "add more rows, by writing '%3 (continued)' here.");
        Problems::issue_problem_end();
        DESTROY(t, table);
        return;
    }

§18.7. Register the names of the new table18.7 = 

    if (Wordings::nonempty(t->table_no_text)) {
        LOGIF(TABLES, "Registering table by number: table %W\n", t->table_no_text);

        word_assemblage wa = PreformUtilities::merge(<table-names-construction>, 0,
            WordAssemblages::from_wording(t->table_no_text));
        wording AW = WordAssemblages::to_wording(&wa);
        Nouns::new_proper_noun(AW, NEUTER_GENDER, ADD_TO_LEXICON_NTOPT,
            TABLE_MC, Rvalues::from_table(t), Task::language_of_syntax());
    }
    if (Wordings::nonempty(t->table_name_text)) {
        LOGIF(TABLES, "Registering table by name: table of %W\n", t->table_name_text);

        word_assemblage wa = PreformUtilities::merge(<table-names-construction>, 1,
                WordAssemblages::from_wording(t->table_name_text));
        wording AW = WordAssemblages::to_wording(&wa);
        Nouns::new_proper_noun(AW, NEUTER_GENDER, ADD_TO_LEXICON_NTOPT,
            TABLE_MC, Rvalues::from_table(t), Task::language_of_syntax());
    }

§18.8. Parse the table's footer for a number of blank rows18.8 = 

    if (<table-footer>(W)) {
        W = GET_RW(<table-footer>, 1);
        switch (<<each>>) {
            case TRUE: t->blank_rows_for_each_text = GET_RW(<table-footer>, 2); break;
            case FALSE: t->blank_rows = <<r>>; break;
            case NOT_APPLICABLE: t->blank_rows = 1;
                t->blank_rows_text = GET_RW(<table-footer>, 2); break;
        }
    }

§18.9. Here's where we start building. The table's representation in the parse tree is currently very unhelpful: it's just one enormous sentence node with all the words in, headings and cells merged together. Instead of using this we hang a list of parse nodes, one for each cell, as children of the entries node for each column.

Count out the rows and columns in the new table18.9 = 

    int pos = Wordings::last_wn(HW)+1;
    while (pos <= Wordings::last_wn(W)) {
        int col_count = 0;
        int row_end = Wordings::last_word_of_formatted_text(Wordings::from(W, pos), FALSE);
        LOGIF(TABLES, "Row %d is %W\n", row_count, Wordings::new(pos, row_end));
        while (pos <= row_end) {
            int cell_end =
                Wordings::last_word_of_formatted_text(Wordings::new(pos, row_end), TRUE);
            LOGIF(TABLES, "Cell (%d, %d) is %W\n",
                row_count, col_count, Wordings::new(pos, cell_end));
            if (row_count == 0) This is a column-heading cell18.9.1
            else This is a data cell18.9.2;
            col_count++;
            pos = cell_end + 1;
        }
        Add implied blank data cells to fill out the row as needed18.9.3;
        row_count++;
    }
    if ((row_count < 2) && (t->blank_rows == 0)) {
        StandardProblems::table_problem(_p_(PM_TableWithoutRows),
            t, NULL, PN, "%1 has no rows.");
        return;
    }

§18.9.1. See "Table Columns" for the actual column creation: note that this makes a node in the parse tree representing the column's use within this table.

This is a column-heading cell18.9.1 = 

    current_sentence = PN;
    wording CW = Wordings::new(pos, cell_end);
    if (col_count == MAX_COLUMNS_PER_TABLE) {
        parse_node *overflow = Diagrams::new_UNPARSED_NOUN(CW);
        int limit = MAX_COLUMNS_PER_TABLE;
        Problems::quote_number(4, &limit);
        StandardProblems::table_problem(_p_(PM_TableTooManyColumns),
            t, NULL, overflow,
            "There are %4 columns in %1 already, and that's the absolute limit, "
            "so the column %3 can't be added.");
    }
    if (col_count < MAX_COLUMNS_PER_TABLE) {
        LOGIF(TABLES, "Creating col %d from '%W'\n", t->no_columns, CW);
        t->columns[t->no_columns] = Tables::Columns::add_to_table(CW, t);
        if (t->columns[t->no_columns].column_identity)  i.e., no Problem occurred
            t->no_columns++;
    }

§18.9.2. Each data cell becomes a node, and is added to the list under its column.

This is a data cell18.9.2 = 

    wording CW = Wordings::new(pos, cell_end);
    parse_node *cell = Diagrams::new_PROPER_NOUN(CW);
    if (col_count >= t->no_columns) {
        current_sentence = PN;
        Problems::quote_number(4, &(row_count));
        int given_col = col_count + 1;  i.e., counting from 1 rather than 0
        Problems::quote_number(5, &(given_col));
        Problems::quote_number(6, &(t->no_columns));
        StandardProblems::table_problem(_p_(PM_TableRowFull),
            t, NULL, cell,
            "In row %4 of the table %1, the entry %3 won't fit, because its row "
            "is already full. (This entry would be in column %5 and the table has "
            "only %6.)");
    } else {
        Annotations::write_int(cell, table_cell_unspecified_ANNOT, FALSE);
        SyntaxTree::graft(Task::syntax_tree(), cell, t->columns[col_count].entries);
    }

§18.9.3. If a row finishes early, we pad it out with blanks.

Add implied blank data cells to fill out the row as needed18.9.3 = 

    while (col_count < t->no_columns) {  which can only happen on data rows
        parse_node *cell = Tables::empty_cell_node();
        Annotations::write_int(cell, table_cell_unspecified_ANNOT, TRUE);
        SyntaxTree::graft(Task::syntax_tree(), cell, t->columns[col_count].entries);
        col_count++;
    }

§18.10. All parsing is finished now.

Act on the connection, possibly destroying the temporary table just made18.10 = 

    table *old_t = existing_table_with_same_name;
    Tables::add_table_contribution(old_t, t->headline_fragment);
    int new_to_old[MAX_COLUMNS_PER_TABLE], old_to_new[MAX_COLUMNS_PER_TABLE];
    Build the column correspondence tables18.10.1;
    switch (connection) {
        case TABLE_IS_CONTINUED: Make the new part a continuation of the existing table18.10.2; break;
        case TABLE_IS_AMENDED: Make the new part an amendment of the existing table18.10.4; break;
        case TABLE_IS_REPLACED: Make the new part a replacement of the existing table18.10.3; break;
        default: internal_error("unknown form of table connection");
    }

§18.10.1. We assume that columns in the new and old tables will be partial permutations of each other: for example the old might have columns "fish", "mammals", "birds" (index j running from 0 to 2) and the new "mammals", "reptiles", "fish", "fungi" (index i running from 0 to 3). We're going to store both the permutation and its inverse, with the index -1 meaning that the column doesn't appear in the other table at all. The result will be: 

    old_to_new: 2, 0, -1
    new_to_old: 1, -1, 0, -1

Build the column correspondence tables18.10.1 = 

    int i, j;
    for (j=0; j<old_t->no_columns; j++) old_to_new[j] = -1;
    for (i=0; i<t->no_columns; i++) new_to_old[i] = -1;
    for (i=0; i<t->no_columns; i++)
        for (j=0; j<old_t->no_columns; j++)
            if (t->columns[i].column_identity == old_t->columns[j].column_identity) {
                new_to_old[i] = j; old_to_new[j] = i;
            }
    LOGIF(TABLES, "Column correspondence table:\n  old->new: ");
    for (j=0; j<old_t->no_columns; j++)
        LOGIF(TABLES, "%d (%W) ", old_to_new[j],
            Nouns::nominative_singular(old_t->columns[j].column_identity->name));
    LOGIF(TABLES, "\n  new->old: ");
    for (i=0; i<t->no_columns; i++)
        LOGIF(TABLES, "%d (%W) ", new_to_old[i],
            Nouns::nominative_singular(t->columns[i].column_identity->name));
    LOGIF(TABLES, "\n");

§18.10.2. We can carry out the continuation immediately, since it just means splicing the new table's rows onto the ends of the old table's columns.

Make the new part a continuation of the existing table18.10.2 = 

    Require that every column of the new table is also found in the old one18.10.2.2;
    Transfer blank rows of the new table to the old one18.10.2.1;
    if (row_count >= 2) {
        int j;
        for (j=0; j<old_t->no_columns; j++)
            if (old_to_new[j] >= 0) {
                SyntaxTree::graft(Task::syntax_tree(),
                    t->columns[old_to_new[j]].entries->down,
                    old_t->columns[j].entries);
            } else {
                int i;
                for (i=1; i<row_count; i++) {  from 1 to omit the column headings
                    parse_node *blank = Tables::empty_cell_node();
                    Annotations::write_int(blank, table_cell_unspecified_ANNOT, TRUE);
                    SyntaxTree::graft(Task::syntax_tree(), blank, old_t->columns[j].entries);
                }
            }
    }
    DESTROY(t, table);

§18.10.2.1. It's a little awkward to work out what the policy is if the original table wants a row for each man, and the continuation wants a row for each woman.

Transfer blank rows of the new table to the old one18.10.2.1 = 

    old_t->blank_rows += t->blank_rows;
    if (Wordings::nonempty(t->blank_rows_for_each_text)) {
        if (Wordings::nonempty(old_t->blank_rows_for_each_text)) {
            current_sentence = t->table_created_at->source_table;
            Problems::quote_table(1, t);
            Problems::quote_table(2, old_t);
            Problems::quote_wording(3, old_t->blank_rows_for_each_text);
            Problems::quote_wording(4, t->blank_rows_for_each_text);
            StandardProblems::handmade_problem(Task::syntax_tree(),
                _p_(PM_TableContinuationContradicts));
            Problems::issue_problem_segment(
                "The table %1 says that it should have a blank row for each "
                "%4, but the original %2 already says it has a blank for each "
                "%3. It can only be specified once.");
            Problems::issue_problem_end();
        }
        old_t->blank_rows_for_each_text = t->blank_rows_for_each_text;
    }

§18.10.3. And similarly for replacements...

Make the new part a replacement of the existing table18.10.3 = 

    Require that every column of the old table is also found in the new one18.10.3.2;
    Copy blank rows of the new table to the old one18.10.3.1;
    int j;
    for (j=0; j<old_t->no_columns; j++)
        if (old_to_new[j] >= 0)  and if this isn't true, we've issued a Problem already
            old_t->columns[j].entries->down
                = t->columns[old_to_new[j]].entries->down;
    int i;
    for (i=0; i<t->no_columns; i++)
        if (new_to_old[i] == -1)
            old_t->columns[old_t->no_columns++] = t->columns[i];  old table must have room
    DESTROY(t, table);

§18.10.3.1. ...but this is easier:

Copy blank rows of the new table to the old one18.10.3.1 = 

    old_t->blank_rows = t->blank_rows;
    old_t->blank_rows_text = t->blank_rows_text;
    old_t->blank_rows_for_each_text = t->blank_rows_for_each_text;

§18.10.4. Amendments can't be done yet, because they depend on recognising values, and it's far too early in Inform's run to recognise constants. So we must postpone the work until later: note that we don't destroy the new table structure in this case.

Make the new part an amendment of the existing table18.10.4 = 

    Require that the old and new tables have exactly matching columns18.10.4.1;
    t->amendment_of = old_t;
    old_t->has_been_amended = TRUE;
    LOGIF(TABLES, "Amendment table created pro tem\n");

§18.10.2.2. Here each new column must appear once in the old table, but the new table doesn't have to cover everything in the old table. (Blanks are used in continuation rows for columns not mentioned.)

Require that every column of the new table is also found in the old one18.10.2.2 = 

    int i, missing = 0;
    for (i=0; i<t->no_columns; i++)
        if (new_to_old[i] == -1)
            missing++;
    if (missing > 0) {
        for (i=0; i<t->no_columns; i++)
            LOG("nto[%d] = %d, otn[%d] = %d\n", i, new_to_old[i], i, old_to_new[i]);
        current_sentence = t->table_created_at->source_table;
        Problems::quote_table(1, t);
        Problems::quote_table(2, old_t);
        if (missing == 1) Problems::quote_text(3, "a column");
        else Problems::quote_text(3, "columns");
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableContinuationAddsCols));
        Problems::issue_problem_segment(
            "The table %1 won't work as a continuation, because it contains "
            "%3 not found in the original %2.");
        Problems::issue_problem_end();
        Display the old and new table column names18.10.2.2.1;
        DESTROY(t, table);
        return;
    }

§18.10.3.2. Here each old column must appear once in the new table, but the new table is allowed to have extra columns. (This means the new table can be "wider" than the old one.)

Require that every column of the old table is also found in the new one18.10.3.2 = 

    int j, missing = 0;
    for (j=0; j<old_t->no_columns; j++)
        if (old_to_new[j] == -1)
            missing++;
    if (missing > 0) {
        current_sentence = t->table_created_at->source_table;
        Problems::quote_table(1, t);
        Problems::quote_table(2, old_t);
        if (missing == 1) Problems::quote_text(3, "a column");
        else Problems::quote_text(3, "columns");
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableReplacementMissesCols));
        Problems::issue_problem_segment(
            "The table %1 won't work as a replacement, because it's missing "
            "%3 found in the original %2.");
        Problems::issue_problem_end();
        Display the old and new table column names18.10.2.2.1;
        DESTROY(t, table);
        return;
    }

§18.10.4.1. We require this to be the identity permutation, i.e., exactly the same columns and in the same order.

Require that the old and new tables have exactly matching columns18.10.4.1 = 

    int mismatch = FALSE;
    if (t->no_columns != old_t->no_columns) mismatch = TRUE;
    int j;
    for (j=0; j<old_t->no_columns; j++)
        if (old_to_new[j] != j)
            mismatch = TRUE;
    if (mismatch) {
        current_sentence = t->table_created_at->source_table;
        Problems::quote_table(1, t);
        Problems::quote_table(2, old_t);
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableAmendmentMisfit));
        Problems::issue_problem_segment(
            "Columns in %1 do not exactly match the original %2. I can only "
            "make changes to rows in an existing table if the amended versions "
            "have the same columns and in the same order.");
        Problems::issue_problem_end();
        Display the old and new table column names18.10.2.2.1;
        DESTROY(t, table);
        return;
    }

§18.10.2.2.1. Display the old and new table column names18.10.2.2.1 = 

    Problems::issue_problem_begin(Task::syntax_tree(), "****");
    Problems::issue_problem_segment("The old table has columns: "); {
        TEMPORARY_TEXT(TEMP)
        int j;
        for (j=0; j<old_t->no_columns; j++) {
            if (j > 0) WRITE_TO(TEMP, ", ");
            WRITE_TO(TEMP, "%+W",
                Nouns::nominative_singular(old_t->columns[j].column_identity->name));
        }
        WRITE_TO(TEMP, ". ");
        Problems::issue_problem_segment_from_stream(TEMP);
        DISCARD_TEXT(TEMP)
    }
    Problems::issue_problem_end();
    Problems::issue_problem_begin(Task::syntax_tree(), "****");
    Problems::issue_problem_segment("The new table has columns: "); {
        TEMPORARY_TEXT(TEMP)
        int i;
        for (i=0; i<t->no_columns; i++) {
            if (i > 0) WRITE_TO(TEMP, ", ");
            WRITE_TO(TEMP, "%+W",
                Nouns::nominative_singular(t->columns[i].column_identity->name));
        }
        WRITE_TO(TEMP, ".");
        Problems::issue_problem_segment_from_stream(TEMP);
        DISCARD_TEXT(TEMP)
    }
    Problems::issue_problem_end();

§19. 

parse_node *Tables::empty_cell_node(void) {
    return Diagrams::new_PROPER_NOUN(EMPTY_WORDING);
}

§20. Table stocking. See also the corresponding code in "Table Sections".

Note that the first column plays a special role in tables used to define new constants, because it holds the names of things which don't exist yet — the things to be defined. So we exempt it from the checking below. 

void Tables::stock_table(table *t, int phase) {
    LOGIF(TABLES, "Stocking $B (%d cols): phase %d\n", t, t->no_columns, phase);
    table_being_examined = t;
    int i = 0;
    if (t->first_column_by_definition) i = 1;
    for (; i<t->no_columns; i++) {
        table_column_usage *tcu = &(t->columns[i]);
        switch (phase) {
            case 1:
                tcu->kind_name_entries = 0;
                tcu->actual_constant_entries = 0;
                tcu->observed_constant_cell = NULL;
                Tables::Columns::check_explicit_headings(t, i, tcu);
                break;
            case 2: {
                int c;
                parse_node *PN;
                for (PN = t->columns[i].entries->down, c = 1; PN; PN = PN->next, c++)
                    if (Wordings::nonempty(Node::get_text(PN)))
                        Tables::stock_table_cell(t, PN, c, i);
                break;
            }
            case 3: Tables::Columns::approve_kind(t, i, tcu);
                break;
        }
    }
}

§21. All of that is delegated to "Table Columns" except for the Tables::stock_table_cell routine, which comes next. It will parse the text of the entry in a cell and act accordingly; the grammar returns one of the following: 

define BLANK_TABLE_ENTRY 1
define SPEC_TABLE_ENTRY 2
define ACTION_TABLE_ENTRY 3
define TOPIC_TABLE_ENTRY 4
define INSTANCE_TABLE_ENTRY 5
define KIND_TABLE_ENTRY 6
define NAMED_CONSTANT_ENTRY 7
define PROBLEMATIC_TABLE_ENTRY -1

§22. Every cell of every table is required to match the following. Perhaps unexpectedly, the syntax doesn't require each entry to be a valid Inform constant; entries can also be blanks, or names of kinds (thus specifying the kind of the table but not the contents), and there are special arrangements for grammar to be understood (in "topic" columns) and for actions written as constants.

Despite appearances, fully general type expressions (such as "open doors", or "number of women") can't legally appear in table cells. The contents have to be constants; the grammar lets more general text through only to let us issue more contextual problem messages. 

<table-cell> ::=
    <table-cell-blank> |       ==> { BLANK_TABLE_ENTRY, Specifications::new_UNKNOWN(W) }
    <k-kind-articled> |        ==> Make anomalous entry for kind22.1
    <s-named-constant> |       ==> { NAMED_CONSTANT_ENTRY, RP[1] }
    <s-global-variable> |      ==> Issue PM_TablePlayerEntry or C20TableVariableEntry problem22.4
    <table-cell-value> |       ==> { pass 1 }
    <list-of-double-quotes> |  ==> Make anomalous entry for text to be understood22.2
    ...                        ==> Issue PM_TableUnknownEntry problem22.5

<table-cell-blank> ::=
    --

<table-cell-value> ::=
    the action of <s-constant-action> |  ==> { ACTION_TABLE_ENTRY, RP[1] }
    <s-constant-action> |                ==> { ACTION_TABLE_ENTRY, RP[1] }
    the action of <s-explicit-action> |  ==> Issue PM_NonconstantActionInTable problem22.3
    <s-explicit-action> |                ==> Issue PM_NonconstantActionInTable problem22.3
    <instance-of-non-object> |           ==> { INSTANCE_TABLE_ENTRY, Rvalues::from_instance(RP[1]) }
    <s-type-expression>                  ==> { SPEC_TABLE_ENTRY, RP[1] }

<list-of-double-quotes> ::=
    <quoted-text> or <list-of-double-quotes> |
    <quoted-text>

§22.1. Make anomalous entry for kind22.1 = 

    parse_node *new = Specifications::from_kind(RP[1]);
    Node::set_text(new, W);
    ==> { KIND_TABLE_ENTRY, new };

§22.2. Make anomalous entry for text to be understood22.2 = 

    parse_node *new = Specifications::from_kind(K_text);
    Node::set_text(new, W);
    ==> { TOPIC_TABLE_ENTRY, new };

§22.3. Issue PM_NonconstantActionInTable problem22.3 = 

    int quoted_col = table_cell_col + 1;  i.e., counting from 1
    Problems::quote_number(4, &quoted_col);
    Problems::quote_wording(5,
        Nouns::nominative_singular(
            table_being_examined->columns[table_cell_col].column_identity->name));
    Problems::quote_number(6, &table_cell_row);
    StandardProblems::table_problem(_p_(PM_NonconstantActionInTable),
        table_being_examined, NULL, table_cell_node,
        "In %1, I'm reading the text %3 in column %4 (%5) of row %6, but this is "
        "an action involving a variable, that is, a value that might vary in play. "
        "%PThis often happens if the action mentions 'the player', for example, "
        "because 'the player' is a variable. If 'the player' is the person "
        "carrying out the action, simply leave those words out; if 'the player' "
        "is involved in some other way, try using 'yourself' instead.");
    ==> { PROBLEMATIC_TABLE_ENTRY, - };

§22.4. The message PM_TablePlayerEntry is so called because by far the commonest case of this is people writing "player" as a constant value in a column of people — it needs to be "yourself" instead, since "player" is a variable.

Issue PM_TablePlayerEntry or C20TableVariableEntry problem22.4 = 

    nonlocal_variable *q = Lvalues::get_nonlocal_variable_if_any(RP[1]);
    if (q == NULL) internal_error("no such variable");
    inference_subject *infs = NonlocalVariables::get_alias(q);
    if (infs) {
        int quoted_col = table_cell_col + 1;  i.e., counting from 1
        Problems::quote_number(4, &quoted_col);
        Problems::quote_wording(5,
            Nouns::nominative_singular(
                table_being_examined->columns[table_cell_col].column_identity->name));
        Problems::quote_number(6, &table_cell_row);
        Problems::quote_subject(7, infs);
        StandardProblems::table_problem(_p_(PM_TablePlayerEntry),
            table_being_examined, NULL, table_cell_node,
            "In %1, the entry %3 in column %4 (%5) of row %6 is the name of a value "
            "which varies, not a constant, and can't be stored as a table entry. %P"
            "This variable is usually set to the constant value '%7', so you might "
            "want to write that instead.");
    } else {
        int quoted_col = table_cell_col + 1;  i.e., counting from 1
        Problems::quote_number(4, &quoted_col);
        Problems::quote_wording(5,
            Nouns::nominative_singular(
                table_being_examined->columns[table_cell_col].column_identity->name));
        Problems::quote_number(6, &table_cell_row);
        StandardProblems::table_problem(_p_(PM_TableVariableEntry),
            table_being_examined, NULL, table_cell_node,
            "In %1, the entry %3 in column %4 (%5) of row %6 is the name of a value "
            "which varies, not a constant, so it can't be stored as a table entry.");
    }
    ==> { PROBLEMATIC_TABLE_ENTRY, - };

§22.5. Issue PM_TableUnknownEntry problem22.5 = 

    Actually issue PM_TableUnknownEntry problem22.5.1;
    ==> { PROBLEMATIC_TABLE_ENTRY, - };

§22.5.1. (There are actually two ways this can happen, which is why it's set out like this.)

Actually issue PM_TableUnknownEntry problem22.5.1 = 

    int quoted_col = table_cell_col + 1;  i.e., counting from 1
    Problems::quote_number(4, &quoted_col);
    Problems::quote_wording(5,
        Nouns::nominative_singular(
            table_being_examined->columns[table_cell_col].column_identity->name));
    Problems::quote_number(6, &table_cell_row);
    StandardProblems::table_problem(_p_(PM_TableUnknownEntry),
        table_being_examined, NULL, table_cell_node,
        "In %1, I'm reading the text %3 in column %4 (%5) of row %6, but I don't "
        "know what this means. %PThis should usually be a value, like a number "
        "or a piece of text, or a blank entry marker '--', but in some circumstances "
        "it can also be an action (such as 'taking the box'), or a kind (such as "
        "'a number') to show what sort of values will go into an otherwise blank "
        "row.");

§23. 

void Tables::stock_table_cell(table *t, parse_node *cell, int row_count, int col_count) {
    current_sentence = cell;
    int topic_exception = FALSE;
    table_cell_node = cell;
    table_cell_row = row_count;
    table_cell_col = col_count;

    Parse the table cell and give it an evaluation as a noun23.1;
    parse_node *evaluation = Node::get_evaluation(cell);
    LOGIF(TABLES, "Cell evaluates to: $P\n", evaluation);

    if (topic_exception == FALSE) Require the cell to evaluate to an actual constant23.2;

    Tables::Columns::note_kind(t, col_count, &(t->columns[col_count]), cell,
        Specifications::to_kind(evaluation), FALSE);
}

§23.1. Parse the table cell and give it an evaluation as a noun23.1 = 

    <table-cell>(Node::get_text(cell));
    parse_node *spec = <<rp>>;
    switch (<<r>>) {
        case BLANK_TABLE_ENTRY:
            Annotations::write_int(cell, table_cell_unspecified_ANNOT, TRUE);
            return;
        case SPEC_TABLE_ENTRY:
            Refiner::give_spec_to_noun(cell, spec);
            break;
        case NAMED_CONSTANT_ENTRY:
            topic_exception = TRUE;
            Refiner::give_spec_to_noun(cell, spec);
            break;
        case INSTANCE_TABLE_ENTRY:
            Refiner::give_spec_to_noun(cell, spec);
            break;
        case KIND_TABLE_ENTRY:
            Annotations::write_int(cell, table_cell_unspecified_ANNOT, TRUE);
            kind *K = Specifications::to_kind(spec);
            Tables::Columns::note_kind(t, col_count, &(t->columns[col_count]), cell,
                K, TRUE);
            return;
        case ACTION_TABLE_ENTRY:
            Refiner::give_spec_to_noun(cell, spec);
            break;
        case TOPIC_TABLE_ENTRY:
            Refiner::give_spec_to_noun(cell, spec);
            topic_exception = TRUE;
            break;
        case PROBLEMATIC_TABLE_ENTRY:
            return;
    }

§23.2. Require the cell to evaluate to an actual constant23.2 = 

    if ((Specifications::is_kind_like(evaluation)) ||
        (Specifications::is_description(evaluation))) {
        LOG("Evaluation is $P\n", evaluation);
        int quoted_col = table_cell_col + 1;  i.e., counting from 1
        Problems::quote_number(4, &quoted_col);
        Problems::quote_wording(5,
            Nouns::nominative_singular(
                table_being_examined->columns[table_cell_col].column_identity->name));
        Problems::quote_number(6, &table_cell_row);
        StandardProblems::table_problem(_p_(PM_TableDescriptionEntry),
            t, NULL, cell,
            "In %1, the entry %3 in column %4 (%5) of row %6 is a general description "
            "of things with no definite value, and can't be stored as a table entry.");
        return;
    }
    if (Node::is(evaluation, CONSTANT_NT) == FALSE) {
        LOG("Evaluation is $P\n", evaluation);
        Actually issue PM_TableUnknownEntry problem22.5.1;
    }

§24. Completing tables. Later on in Inform's run, just before compiling the tables, we call this: 

void Tables::complete(void) {
    Finally make any table amendments which have been called for24.1;
    Create blank rows described textually, if they were24.2;
    Create blank rows for each instance of a kind, if requested24.3;
}

§24.1. For the actual code, see below.

Finally make any table amendments which have been called for24.1 = 

    table *t;
    LOOP_OVER(t, table)
        if (t->amendment_of)
            Tables::amend_table(t->amendment_of, t);

§24.2. Create blank rows described textually, if they were24.2 = 

    table *t;
    LOOP_OVER(t, table)
        if (t->amendment_of == FALSE) {
            current_sentence = t->table_created_at->source_table;
            wording W = t->blank_rows_text;
            int N = -1;
            if (Wordings::nonempty(W)) {
                if (<s-named-constant>(W)) {
                    parse_node *val = NonlocalVariables::substitute_constants(<<rp>>);
                    N = Rvalues::to_int(val);
                }
                if (N >= 0) t->blank_rows = N;
                else {
                    Problems::quote_wording(4, t->blank_rows_text);
                    StandardProblems::table_problem(_p_(PM_TableUnknownBlanks),
                        t, NULL, current_sentence,
                        "%1 asked to have '%4' extra blank rows, but that would "
                        "only make sense for a literal number like '15' or a "
                        "name for a constant number. (The number must of course "
                        "be 0 or more.)");
                }
            }
        }

§24.3. Create blank rows for each instance of a kind, if requested24.3 = 

    table *t;
    LOOP_OVER(t, table)
        if (t->amendment_of == FALSE) {
            current_sentence = t->table_created_at->source_table;
            if (Wordings::nonempty(t->blank_rows_for_each_text)) {
                kind *K = NULL;
                if (<k-kind>(t->blank_rows_for_each_text)) {
                    K = <<rp>>;
                    t->blank_rows += Instances::count(K);
                } else {
                    Problems::quote_wording(4, t->blank_rows_for_each_text);
                    StandardProblems::table_problem(_p_(PM_TableKindlessBlanks),
                        t, NULL, current_sentence,
                        "%1 asked to have extra blank rows for each '%4', but that "
                        "isn't a kind, so I can't see how many blank rows to make.");
                }
            }
        }

§25. Amending tables. Unlike continuations and replacements, table amendments depend on actual values written into the cells, which means they can't be performed early in the run. So for quite a long time two table structures exist: the "main table", the actual one which will exist in play; and the "amendments" table, which is a structure holding the amendment lines, but which won't actually exist independently at run-time. The following routine is where the rows from the amendments table are used to modify the main table, after which the amendments table has no further use.

As might be expected, we work down the amendments table and apply them one at a time: 

void Tables::amend_table(table *main_table, table *amendments) {
    LOGIF(TABLES, "Amending table $B according to $B\n", main_table, amendments);
    parse_node *leftmost_amend_cell = NULL;
    int amend_row = 1, amendment_problem_opened = FALSE;
    for (amend_row = 1, leftmost_amend_cell = amendments->columns[0].entries->down;
        leftmost_amend_cell;
        amend_row++, leftmost_amend_cell = leftmost_amend_cell->next)
        Apply the amendment in this row to the main table25.1;
}

§25.1. The following is not so obvious. The amendment row is intended to replace a row in the main table, and we need to decide which one. Suppose the amendment reads: 

    62   "lampstand"   10:30 AM

If the main table has exactly one row with 62 in the first column, we choose that; if it contains more than one, we look for rows which begin with 62 and then "lampstand"; and so on. (Recall that amendment tables have exactly the same columns as their originals, and in the same order.)

In the following, col is the rightmost column used in the initial string being tried: so when it's 0, we're just trying to match 62, when it's 1 we're trying to match 62 and "lampstand"; and so on. But of course each such search is narrower than the one before, so we only need to look at the rows which passed last time, and test their values in column col.

In fact, we do this in reverse: we start with every row in the main table marked as a possible match, and then exclude rows as they fail to match. Eventually this should leave only a single row, and that's the winner.

Apply the amendment in this row to the main table25.1 = 

    int col, matches_in_last_round = 0;
    Mark every row in the main table as a possible match25.1.1;
    for (col = 0; col < main_table->no_columns; col++) {
        parse_node *amend_cell;
        Set the amend-cell to this column's cell in the current amendment row25.1.2;
        if (Annotations::read_int(amend_cell, table_cell_unspecified_ANNOT) == FALSE) {
            int only_row_left = -1;
            Use the key value in the amend-cell to make an amendment25.1.3;
            if (only_row_left >= 0) {
                Tables::splice_table_row(main_table, amendments, only_row_left, amend_row);
                break;
            }
        }
    }

§25.1.1. We need one flag for each row in the main table; we do this with the "row amendable" annotation for the cell nodes in the first column. (There's nothing special about the first column, but it's guaranteed to exist, i.e., there is always at least one column.)

Mark every row in the main table as a possible match25.1.1 = 

    parse_node *leftmost_cell;
    for (leftmost_cell = main_table->columns[0].entries->down;
        leftmost_cell;
        leftmost_cell = leftmost_cell->next) {
        Annotations::write_int(leftmost_cell, row_amendable_ANNOT, TRUE);
        matches_in_last_round++;
    }

§25.1.2. Set the amend-cell to this column's cell in the current amendment row25.1.2 = 

    int i;
    for (i = 1, amend_cell = amendments->columns[col].entries->down;
        amend_cell && (i < amend_row); i++, amend_cell = amend_cell->next) ;
    if (amend_cell == NULL) internal_error("columns in amendments aren't equal in length");

§25.1.3. When we get here, then, we look at the key value in the amend-cell: suppose this is the number 17. If there's no row in the main table having 17 in this column, we're stuck. But if there are two or more, we allow the loop to move us along to the next column, hoping that the key value there will find a unique match. If we're in the last column and there are still multiple possibilities, the amendment row must be identical to more than one row of the main table — in this case the amendment will have no effect, but put another way, it can do no harm.

Use the key value in the amend-cell to make an amendment25.1.3 = 

    parse_node *amend_key = Node::get_evaluation(amend_cell);
    LOGIF(TABLES, "Amend row %d, col %d, key $P: $T\n", amend_row, col, amend_key, amend_cell);
    if (Node::is(amend_key, CONSTANT_NT) == FALSE)
        internal_error("bad key in amendments table");  code above should make this impossible

    int matches = 0;
    Find the number of possible-match rows in the main table with this key value in the same column25.1.3.1;
    if (matches == 0) Issue problem to say that no row in the main table matches25.1.3.2;
    if (matches > 1) {
        if (col < main_table->no_columns - 1)  i.e., if we haven't reached the final column
            only_row_left = -1;  because there's no single row left
    }
    matches_in_last_round = matches;

§25.1.3.1. The loop below and its inner conditional look pretty forbidding, but they come down to this: loop through each row of the main table which is still a possible match.

Find the number of possible-match rows in the main table with this key value in the same column25.1.3.1 = 

    int row;
    parse_node *leftmost_cell;
    parse_node *main_cell;
    for (row = 1,
        main_cell = main_table->columns[col].entries->down,
        leftmost_cell = main_table->columns[0].entries->down;
        main_cell;
        row++,
        main_cell = main_cell->next,
        leftmost_cell = leftmost_cell->next) {
        parse_node *main_value = Node::get_evaluation(main_cell);
        if (Annotations::read_int(leftmost_cell, row_amendable_ANNOT))
            See if this possible-match row has the right key value in the new column25.1.3.1.1;
    }

§25.1.3.1.1. We not only record the result if there's a match; we kick the row out of the possible-match set if there isn't.

See if this possible-match row has the right key value in the new column25.1.3.1.1 = 

    LOG("Key in row %d is $P\n", row, main_value);
    if ((Node::is(main_value, CONSTANT_NT)) &&
        (Rvalues::compare_CONSTANT(amend_key, main_value))) {
        matches++;
        only_row_left = row;
    } else {
        Annotations::write_int(leftmost_cell, row_amendable_ANNOT, FALSE);
    }

§25.1.3.2. That just leaves the problem message, a very subtle one which took a long time to find a clear wording for:

Issue problem to say that no row in the main table matches25.1.3.2 = 

    Begin an amendment problem message25.1.3.2.1;
    int quoted_col = col + 1;  i.e., counting from 1, not 0
    Problems::quote_number(1, &amend_row);
    Problems::quote_number(2, &quoted_col);
    Problems::quote_source(3, amend_cell);
    Problems::quote_wording(4,
        Nouns::nominative_singular(main_table->columns[col].column_identity->name));
    Problems::quote_table(5, main_table);
    Problems::quote_number(6, &matches_in_last_round);
    if (matches_in_last_round > 2) Problems::quote_text(7, "any");
    else Problems::quote_text(7, "either");
    Problems::issue_problem_begin(Task::syntax_tree(), "****");
    if (col == 0)
    Problems::issue_problem_segment(
        "(Amendment %1). I can't match this to any row - there's nothing with "
        "an entry of %3 in the lefthand column (%4).");
    else
    Problems::issue_problem_segment(
        "(Amendment %1). I can't decide which row this should replace. "
        "It matches %6 rows until I get up to column %2 (%4), but then "
        "it reads %3, which is different from %7 of them.");
    Problems::issue_problem_end();
    break;  to move on to the next row in the amendments

§25.1.3.2.1. Begin an amendment problem message25.1.3.2.1 = 

    if (amendment_problem_opened == FALSE) {
        amendment_problem_opened = TRUE;
        current_sentence = amendments->table_created_at->source_table;
        Problems::quote_table(1, main_table);
        Problems::quote_table(2, amendments);
        StandardProblems::handmade_problem(Task::syntax_tree(),
            _p_(PM_TableAmendmentMismatch));
        Problems::issue_problem_segment(
            "I'm currently trying to amend rows in %1 according to the instructions "
            "in %2. To do that, I have to match each amendment row in turn, which "
            "I do by trying to match up entries in the leftmost column(s).");
        Problems::issue_problem_end();
        Problems::issue_problem_begin(Task::syntax_tree(), "****");
        Problems::issue_problem_segment("But I ran into problems:");
        Problems::issue_problem_end();
    }

§26. And, of course, the actual splicing of the amendment row in place of the original: 

void Tables::splice_table_row(table *table_to, table *table_from, int row_to, int row_from) {
    int i;
    for (i=0; i<table_to->no_columns; i++) {
        parse_node *cell_to, *cell_from;
        int row;
        for (row = 1, cell_to = table_to->columns[i].entries->down;
                cell_to && (row < row_to); cell_to = cell_to->next, row++) ;
        for (row = 1, cell_from = table_from->columns[i].entries->down;
                cell_from && (row < row_from); cell_from = cell_from->next, row++) ;
        if ((cell_to) && (cell_from)) {
            Refiner::copy_noun_details(cell_to, cell_from);
            Annotations::write_int(cell_to, table_cell_unspecified_ANNOT,
                Annotations::read_int(cell_from, table_cell_unspecified_ANNOT));
        } else internal_error("bad table row splice");
    }
}

§27. This is called when a table is being asked to define objects (or kinds). 

void Tables::use_to_define(table *t, int defining_objects, parse_node *where) {
    if (t == NULL) internal_error("no table");
    if (defining_objects == FALSE) {
        t->contains_property_values_at_run_time = TRUE;
        t->fill_in_blanks = TRUE;
        t->preserve_row_order_at_run_time = TRUE;
        t->disable_block_constant_correction = TRUE;
    }
    if ((t->has_been_amended) && (defining_objects))
        StandardProblems::sentence_problem(Task::syntax_tree(),
            _p_(PM_TableCantDefineAndAmend),
            "you can't use 'defined by' to define objects using a table "
            "which is amended by another table",
            "since that could too easily lead to ambiguities about what "
            "the property values are.");
    t->first_column_by_definition = TRUE;
    t->where_used_to_define = where;
}