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< ul class = "crumbs" > < li > < a href = "../index.html" > Home< / a > < / li > < li > < a href = "../services.html" > Services< / a > < / li > < li > < a href = "index.html" > words< / a > < / li > < li > < a href = "index.html#4" > Chapter 4: Parsing< / a > < / li > < li > < b > Length Extremes< / b > < / li > < / ul > < / div >
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< p class = "purpose" > To precalculate data which enables rapid parsing of source text against a Preform grammar.< / p >
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< p class = "commentary firstcommentary" > < a id = "SP1" class = "paragraph-anchor" > < / a > < b > § 1. < / b > The "length extremes" system provides one of two optimisations enabling
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the Preform parser quickly to reject non-matches, the other being
< a href = "4-ni.html" class = "internal" > Nonterminal Incidences< / a > , which is harder to understand.
< / p >
< p class = "commentary" > It may elucidate both to see the actual optimisation data for nonterminals
as used in a typical run of Inform 7 — see < a href = "../inform7/M-pm.html" class = "internal" > Performance Metrics (in inform7)< / a > .
< / p >
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< p class = "commentary firstcommentary" > < a id = "SP2" class = "paragraph-anchor" > < / a > < b > § 2. < / b > The "extremes" of something to be matched against are the minimum and maximum
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number of words in a successful match; with < span class = "extract" > < span class = "extract-syntax" > INFINITE_WORD_COUNT< / span > < / span > as maximum
where the number is unlimited.
< / p >
< pre class = "definitions code-font" > < span class = "definition-keyword" > define< / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > < / span > < span class = "constant-syntax" > 1000000000< / span >
< / pre >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > typedef< / span > < span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > struct< / span > < span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > min_words< / span > < span class = "plain-syntax" > , < / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > } < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > ;< / span >
< / pre >
< ul class = "endnotetexts" > < li > The structure length_extremes is accessed in 4/to, 4/ni, 4/prf, 4/ins and here.< / li > < / ul >
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< p class = "commentary firstcommentary" > < a id = "SP3" class = "paragraph-anchor" > < / a > < b > § 3. < / b > < / p >
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< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::new< / span > < button class = "popup" onclick = "togglePopup('usagePopup1')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup1" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::new< / span > < / span > :< br / > Nonterminals - < a href = "4-nnt.html#SP4" > § 4< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > min< / span > < span class = "plain-syntax" > , < / span > < span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > max< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > min< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > max< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP4" class = "paragraph-anchor" > < / a > < b > § 4. < / b > Four useful special cases:
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< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::no_words_at_all< / span > < button class = "popup" onclick = "togglePopup('usagePopup2')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup2" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::no_words_at_all< / span > < / span > :< br / > < a href = "4-le.html#SP8" > § 8< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 0< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 0< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::any_number_of_words< / span > < button class = "popup" onclick = "togglePopup('usagePopup3')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup3" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::any_number_of_words< / span > < / span > :< br / > < a href = "4-le.html#SP9" > § 9< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 0< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::at_least_one_word< / span > < button class = "popup" onclick = "togglePopup('usagePopup4')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup4" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::at_least_one_word< / span > < / span > :< br / > < a href = "4-le.html#SP9" > § 9< / a > < br / > The Optimiser - < a href = "4-to.html#SP2" > § 2< / a > , < a href = "4-to.html#SP4" > § 4< / a > , < a href = "4-to.html#SP7" > § 7< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 1< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::exactly_one_word< / span > < button class = "popup" onclick = "togglePopup('usagePopup5')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup5" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::exactly_one_word< / span > < / span > :< br / > < a href = "4-le.html#SP9" > § 9< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > void< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 1< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > 1< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP5" class = "paragraph-anchor" > < / a > < b > § 5. < / b > Testing:
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< / p >
< pre class = "displayed-code all-displayed-code code-font" >
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< span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::in_bounds< / span > < button class = "popup" onclick = "togglePopup('usagePopup6')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup6" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::in_bounds< / span > < / span > :< br / > Preform - < a href = "4-prf.html#SP1" > § 1< / a > , < a href = "4-prf.html#SP1_3_2_1" > § 1.3.2.1< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > match_length< / span > < span class = "plain-syntax" > , < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ) {< / span >
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< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > ((< / span > < span class = "identifier-syntax" > match_length< / span > < span class = "plain-syntax" > > = < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > ) & & (< / span > < span class = "identifier-syntax" > match_length< / span > < span class = "plain-syntax" > < = < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > ))< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > TRUE< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > FALSE< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP6" class = "paragraph-anchor" > < / a > < b > § 6. < / b > Concatenation produces the length extremes for the text X followed by the
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text Y:
< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::concatenate< / span > < button class = "popup" onclick = "togglePopup('usagePopup7')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup7" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::concatenate< / span > < / span > :< br / > < a href = "4-le.html#SP8" > § 8< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E_X< / span > < span class = "plain-syntax" > , < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > E_X< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > += < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > min_words< / span > < span class = "plain-syntax" > > < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ) < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > += < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > > < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ) < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "constant-syntax" > INFINITE_WORD_COUNT< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP7" class = "paragraph-anchor" > < / a > < b > § 7. < / b > The union provides the wider bounds, whichever they are:
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< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::union< / span > < button class = "popup" onclick = "togglePopup('usagePopup8')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup8" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::union< / span > < / span > :< br / > < a href = "4-le.html#SP8" > § 8< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E_X< / span > < span class = "plain-syntax" > , < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > E_X< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > < < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > ) < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > min_words< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > ) < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > E_Y< / span > < span class = "plain-syntax" > .< / span > < span class = "identifier-syntax" > max_words< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP8" class = "paragraph-anchor" > < / a > < b > § 8. < / b > The minimum matched text length for a nonterminal is the smallest of the
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minima for its possible productions; for a production, it's the sum of the
minimum match lengths of its tokens.
< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::calculate_for_nt< / span > < button class = "popup" onclick = "togglePopup('usagePopup9')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup9" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::calculate_for_nt< / span > < / span > :< br / > The Optimiser - < a href = "4-to.html#SP8" > § 8< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > nonterminal< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > nt< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::no_words_at_all< / span > < / a > < span class = "plain-syntax" > ();< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > int< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > first< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > TRUE< / span > < span class = "plain-syntax" > ;< / span >
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< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > for< / span > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > production_list< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > pl< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > nt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > first_pl< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pl< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pl< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pl< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > next_pl< / span > < span class = "plain-syntax" > )< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > for< / span > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > production< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pl< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > first_pr< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > next_pr< / span > < span class = "plain-syntax" > ) {< / span >
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< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > opt< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > pr_extremes< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP8" class = "function-link" > < span class = "function-syntax" > LengthExtremes::calculate_for_pr< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > );< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > first< / span > < span class = "plain-syntax" > ) { < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > -> < / span > < span class = "identifier-syntax" > opt< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > pr_extremes< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > first< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > FALSE< / span > < span class = "plain-syntax" > ; }< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > else< / span > < span class = "plain-syntax" > { < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP7" class = "function-link" > < span class = "function-syntax" > LengthExtremes::union< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > , < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > opt< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > pr_extremes< / span > < span class = "plain-syntax" > ); }< / span >
< span class = "plain-syntax" > }< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::calculate_for_pr< / span > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > production< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::no_words_at_all< / span > < / a > < span class = "plain-syntax" > ();< / span >
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< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > for< / span > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > ptoken< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pr< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > first_pt< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > ; < / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > next_pt< / span > < span class = "plain-syntax" > )< / span >
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< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP6" class = "function-link" > < span class = "function-syntax" > LengthExtremes::concatenate< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > , < / span > < a href = "4-le.html#SP9" class = "function-link" > < span class = "function-syntax" > LengthExtremes::calculate_for_pt< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > ));< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
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< p class = "commentary firstcommentary" > < a id = "SP9" class = "paragraph-anchor" > < / a > < b > § 9. < / b > An interesting point here is that the negation of a ptoken can in principle
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have any length, except that we specified < span class = "extract" > < span class = "extract-syntax" > ^ example< / span > < / span > to match only a single
word — any word other than "example". So the extremes for < span class = "extract" > < span class = "extract-syntax" > ^ example< / span > < / span > are
1 and 1, whereas for < span class = "extract" > < span class = "extract-syntax" > ^ < sample-nonterminal> < / span > < / span > they would have to be 0 and
infinity.
< / p >
< pre class = "displayed-code all-displayed-code code-font" >
< span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "function-syntax" > LengthExtremes::calculate_for_pt< / span > < button class = "popup" onclick = "togglePopup('usagePopup10')" > < span class = "comment-syntax" > ?< / span > < span class = "popuptext" id = "usagePopup10" > Usage of < span class = "code-font" > < span class = "function-syntax" > LengthExtremes::calculate_for_pt< / span > < / span > :< br / > < a href = "4-le.html#SP8" > § 8< / a > < br / > The Optimiser - < a href = "4-to.html#SP9" > § 9< / a > < / span > < / button > < span class = "plain-syntax" > (< / span > < span class = "reserved-syntax" > ptoken< / span > < span class = "plain-syntax" > *< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > length_extremes< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::exactly_one_word< / span > < / a > < span class = "plain-syntax" > ();< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > negated_ptoken< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > if< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > ptoken_category< / span > < span class = "plain-syntax" > != < / span > < span class = "constant-syntax" > FIXED_WORD_PTC< / span > < span class = "plain-syntax" > )< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::any_number_of_words< / span > < / a > < span class = "plain-syntax" > ();< / span >
< span class = "plain-syntax" > } < / span > < span class = "reserved-syntax" > else< / span > < span class = "plain-syntax" > {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > switch< / span > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > ptoken_category< / span > < span class = "plain-syntax" > ) {< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > case< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > NONTERMINAL_PTC:< / span >
< span class = "plain-syntax" > < / span > < a href = "4-to.html#SP8" class = "function-link" > < span class = "function-syntax" > Optimiser::optimise_nonterminal< / span > < / a > < span class = "plain-syntax" > (< / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > nt_pt< / span > < span class = "plain-syntax" > ); < / span > < span class = "comment-syntax" > recurse as needed< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < span class = "identifier-syntax" > pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > nt_pt< / span > < span class = "plain-syntax" > -> < / span > < span class = "element-syntax" > opt< / span > < span class = "plain-syntax" > .< / span > < span class = "element-syntax" > nt_extremes< / span > < span class = "plain-syntax" > ; < / span > < span class = "reserved-syntax" > break< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > case< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > MULTIPLE_WILDCARD_PTC:< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::at_least_one_word< / span > < / a > < span class = "plain-syntax" > (); < / span > < span class = "reserved-syntax" > break< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > case< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > POSSIBLY_EMPTY_WILDCARD_PTC:< / span >
< span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > = < / span > < a href = "4-le.html#SP4" class = "function-link" > < span class = "function-syntax" > LengthExtremes::any_number_of_words< / span > < / a > < span class = "plain-syntax" > (); < / span > < span class = "reserved-syntax" > break< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< span class = "plain-syntax" > }< / span >
< span class = "plain-syntax" > < / span > < span class = "reserved-syntax" > return< / span > < span class = "plain-syntax" > < / span > < span class = "identifier-syntax" > E< / span > < span class = "plain-syntax" > ;< / span >
< span class = "plain-syntax" > }< / span >
< / pre >
< nav role = "progress" > < div class = "progresscontainer" >
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< ul class = "progressbar" > < li class = "progressprev" > < a href = "4-to.html" > ❮ < / a > < / li > < li class = "progresschapter" > < a href = "P-wtmd.html" > P< / a > < / li > < li class = "progresschapter" > < a href = "1-wm.html" > 1< / a > < / li > < li class = "progresschapter" > < a href = "2-vcb.html" > 2< / a > < / li > < li class = "progresschapter" > < a href = "3-lxr.html" > 3< / a > < / li > < li class = "progresscurrentchapter" > 4< / li > < li class = "progresssection" > < a href = "4-ap.html" > ap< / a > < / li > < li class = "progresssection" > < a href = "4-nnt.html" > nnt< / a > < / li > < li class = "progresssection" > < a href = "4-lp.html" > lp< / a > < / li > < li class = "progresssection" > < a href = "4-to.html" > to< / a > < / li > < li class = "progresscurrent" > le< / li > < li class = "progresssection" > < a href = "4-ni.html" > ni< / a > < / li > < li class = "progresssection" > < a href = "4-prf.html" > prf< / a > < / li > < li class = "progresssection" > < a href = "4-bn.html" > bn< / a > < / li > < li class = "progresssection" > < a href = "4-ins.html" > ins< / a > < / li > < li class = "progresssection" > < a href = "4-pu.html" > pu< / a > < / li > < li class = "progressnext" > < a href = "4-ni.html" > ❯ < / a > < / li > < / ul > < / div >
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< / nav > <!-- End of weave -->
< / main >
< / body >
< / html >