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114 lines
3 KiB
OpenEdge ABL
114 lines
3 KiB
OpenEdge ABL
[BasicNT::] Basic Nonterminals.
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A handful of bare minimum Preform syntax.
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@h Nonterminal names.
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This is a typical internal nonterminal being defined, though it's a bit more
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meta than most -- it's a nonterminal which matches against the name of any
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nonterminal. (This is used only to parse inclusion requests for the debugging
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log.)
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Note that we use the |internal 1| to signal that a correct match must have
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exactly one word.
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=
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<preform-nonterminal> internal 1 {
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nonterminal *nt = Nonterminals::detect(Lexer::word(Wordings::first_wn(W)));
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if (nt) { ==> { -, nt }; return TRUE; }
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==> { fail nonterminal };
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}
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@h Text positions.
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A useful nonterminal which matches no text, but detects the position:
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=
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<if-start-of-paragraph> internal 0 {
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int w1 = Wordings::first_wn(W);
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if ((w1 == 0) || (compare_word(w1-1, PARBREAK_V))) return TRUE;
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==> { fail nonterminal };
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}
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@ And another convenience:
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=
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<if-not-cap> internal 0 {
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int w1 = Wordings::first_wn(W);
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if (Word::unexpectedly_upper_case(w1) == FALSE) return TRUE;
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==> { fail nonterminal };
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}
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@h Balancing.
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The following regular (not internal!) nonterminal matches any text in which
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braces and brackets are correctly paired.
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=
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<balanced-text> ::=
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......
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@ Inform contains relatively few syntaxes where commas are actually required,
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though they can optionally be used in many lists, as here:
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>> parma ham, camembert, grapes
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But for when we only want to spot comma placements, this can be used. Note
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that the comma matches only if not in brackets.
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=
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<list-comma-division> ::=
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...... , ......
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@h Literal numbers.
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(Inform itself doesn't use this, but has alternatives for cardinals and
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ordinals within the VM-representable range.)
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=
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<any-integer> internal 1 {
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if (Vocabulary::test_flags(Wordings::first_wn(W), NUMBER_MC)) {
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int N = Vocabulary::get_literal_number_value(Lexer::word(Wordings::first_wn(W)));
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==> { N, - };
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return TRUE;
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}
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==> { fail nonterminal };
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}
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@h Literal text.
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Text is "with substitutions" if it contains square brackets, used in Inform
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for interpolations called "text substitutions".
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<quoted-text> internal 1 {
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if ((Wordings::nonempty(W)) &&
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(Vocabulary::test_flags(Wordings::first_wn(W), TEXT_MC+TEXTWITHSUBS_MC))) {
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==> { Wordings::first_wn(W), - }; return TRUE;
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}
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==> { fail nonterminal };
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}
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<quoted-text-with-subs> internal 1 {
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if ((Wordings::nonempty(W)) &&
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(Vocabulary::test_flags(Wordings::first_wn(W), TEXTWITHSUBS_MC))) {
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==> { Wordings::first_wn(W), - }; return TRUE;
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}
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==> { fail nonterminal };
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}
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<quoted-text-without-subs> internal 1 {
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if ((Wordings::nonempty(W)) &&
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(Vocabulary::test_flags(Wordings::first_wn(W), TEXT_MC))) {
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==> { Wordings::first_wn(W), - }; return TRUE;
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}
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==> { fail nonterminal };
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}
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@ For finicky technical reasons the easiest way to detect an empty piece
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of text |""| is to provide a nonterminal matching it:
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=
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<empty-text> internal 1 {
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if ((Wordings::nonempty(W)) &&
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(Word::compare_by_strcmp(Wordings::first_wn(W), L"\"\""))) {
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==> { Wordings::first_wn(W), - }; return TRUE;
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}
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==> { fail nonterminal };
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}
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