226 lines
6.9 KiB
C++
226 lines
6.9 KiB
C++
/* Copyright (C) 2004 J.F.Dockes
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the
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* Free Software Foundation, Inc.,
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* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*/
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#ifndef _TEXTSPLIT_H_INCLUDED_
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#define _TEXTSPLIT_H_INCLUDED_
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#include <math.h>
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#include <string>
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#include <vector>
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using std::string;
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using std::vector;
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using std::pair;
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class Utf8Iter;
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/**
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* Split text into words.
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* See comments at top of .cpp for more explanations.
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* This uses a callback function. It could be done with an iterator instead,
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* but 'ts much simpler this way...
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*/
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class TextSplit {
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public:
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// Should we activate special processing of Chinese characters ? This
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// needs a little more cpu, so it can be turned off globally. This is set
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// by rclconfig, changing it means reindexing
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static bool o_processCJK;
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static unsigned int o_CJKNgramLen;
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static const unsigned int o_CJKMaxNgramLen = 5;
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static void cjkProcessing(bool onoff, unsigned int ngramlen = 2)
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{
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o_processCJK = onoff;
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o_CJKNgramLen = ngramlen <= o_CJKMaxNgramLen ?
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ngramlen : o_CJKMaxNgramLen;
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}
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// Are we indexing numbers ? Set by rclconfig. Change needs reindex
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static bool o_noNumbers;
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static void noNumbers()
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{
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o_noNumbers = true;
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}
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enum Flags {
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// Default: will return spans and words (a_b, a, b)
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TXTS_NONE = 0,
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// Only return maximum spans (a@b.com, not a, b, or com)
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TXTS_ONLYSPANS = 1,
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// Special: Only return atomic words (a, b, com). This is not
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// used for indexing, but for position computation during
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// abstract generation,
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TXTS_NOSPANS = 2,
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// Handle wildcards as letters. This is used with ONLYSPANS
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// for parsing a user query (never alone).
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TXTS_KEEPWILD = 4
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};
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TextSplit(Flags flags = Flags(TXTS_NONE))
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: m_flags(flags), m_maxWordLength(40), m_prevpos(-1)
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{
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}
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virtual ~TextSplit() {}
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virtual void setMaxWordLength(int l)
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{
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m_maxWordLength = l;
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}
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/** Split text, emit words and positions. */
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virtual bool text_to_words(const string &in);
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/** Process one output word: to be implemented by the actual user class */
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virtual bool takeword(const string& term,
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int pos, // term pos
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int bts, // byte offset of first char in term
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int bte // byte offset of first char after term
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) = 0;
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/** Called when we encounter formfeed \f 0x0c. Override to use the event.
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* Mostly or exclusively used with pdftoxx output. Other filters mostly
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* just don't know about pages. */
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virtual void newpage(int /*pos*/)
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{
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}
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// Static utility functions:
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/** Count words in string, as the splitter would generate them */
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static int countWords(const string &in, Flags flgs = TXTS_ONLYSPANS);
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/** Check if this is visibly not a single block of text */
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static bool hasVisibleWhite(const string &in);
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/** Split text span into strings, at white space, allowing for substrings
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* quoted with " . Escaping with \ works as usual inside the quoted areas.
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* This has to be kept separate from smallut.cpp's stringsToStrings, which
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* basically works only if whitespace is ascii, and which processes
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* non-utf-8 input (iso-8859 config files work ok). This hopefully
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* handles all Unicode whitespace, but needs correct utf-8 input
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*/
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static bool stringToStrings(const string &s, vector<string> &tokens);
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/** Is char CJK ? */
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static bool isCJK(int c);
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/** Statistics about word length (average and dispersion) can
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* detect bad data like undecoded base64 or other mis-identified
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* pieces of data taken as text. In practise, this keeps some junk out
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* of the index, but does not decrease the index size much, and is
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* probably not worth the trouble in general. Code kept because it
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* probably can be useful in special cases. Base64 data does has
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* word separators in it (+/) and is characterised by high average
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* word length (>10, often close to 20) and high word length
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* dispersion (avg/sigma > 0.8). In my tests, most natural
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* language text has average word lengths around 5-8 and avg/sigma
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* < 0.7
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*/
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#ifdef TEXTSPLIT_STATS
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class Stats {
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public:
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Stats()
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{
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reset();
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}
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void reset()
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{
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count = 0;
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totlen = 0;
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sigma_acc = 0;
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}
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void newsamp(unsigned int len)
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{
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++count;
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totlen += len;
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double avglen = double(totlen) / double(count);
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sigma_acc += (avglen - len) * (avglen - len);
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}
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struct Values {
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int count;
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double avglen;
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double sigma;
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};
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Values get()
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{
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Values v;
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v.count = count;
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v.avglen = double(totlen) / double(count);
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v.sigma = sqrt(sigma_acc / count);
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return v;
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}
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private:
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int count;
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int totlen;
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double sigma_acc;
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};
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Stats::Values getStats()
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{
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return m_stats.get();
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}
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void resetStats()
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{
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m_stats.reset();
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}
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#endif // TEXTSPLIT_STATS
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private:
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Flags m_flags;
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int m_maxWordLength;
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// Current span. Might be jf.dockes@wanadoo.f
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string m_span;
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vector <pair<unsigned int, unsigned int> > m_words_in_span;
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// Current word: no punctuation at all in there. Byte offset
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// relative to the current span and byte length
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int m_wordStart;
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unsigned int m_wordLen;
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// Currently inside number
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bool m_inNumber;
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// Term position of current word and span
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int m_wordpos;
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int m_spanpos;
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// It may happen that our cleanup would result in emitting the
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// same term twice. We try to avoid this
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int m_prevpos;
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unsigned int m_prevlen;
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#ifdef TEXTSPLIT_STATS
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// Stats counters. These are processed in TextSplit rather than by a
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// TermProc so that we can take very long words (not emitted) into
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// account.
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Stats m_stats;
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#endif
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// Word length in characters. Declared but not updated if !TEXTSPLIT_STATS
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unsigned int m_wordChars;
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// This processes cjk text:
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bool cjk_to_words(Utf8Iter *it, unsigned int *cp);
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bool emitterm(bool isspan, string &term, int pos, int bs, int be);
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bool doemit(bool spanerase, int bp);
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void discardspan();
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bool span_is_acronym(std::string *acronym);
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bool words_from_span(int bp);
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};
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#endif /* _TEXTSPLIT_H_INCLUDED_ */
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