125 lines
3.9 KiB
C#
125 lines
3.9 KiB
C#
/*
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* BotSharp.NLP Library
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* Copyright (C) 2018 Haiping Chen
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*
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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 3 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, see <http://www.gnu.org/licenses/>.
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*/
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using System;
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using System.Collections.Generic;
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using System.Linq;
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using System.Text;
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using System.Text.RegularExpressions;
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namespace BotSharp.NLP.Tokenize
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{
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/// <summary>
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/// Regular-Expression Tokenizers
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/// </summary>
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public class RegexTokenizer : ITokenizer
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{
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/// <summary>
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/// Tokenize a text into a sequence of alphabetic and non-alphabetic characters
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/// </summary>
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public const string WORD_PUNC = @"[^\w\s]+|\w+";
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/// <summary>
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/// Tokenize a string, treating any sequence of blank lines as a delimiter.
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/// Blank lines are defined as lines containing no characters, except for space or tab characters.
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/// options.IsGap = true
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/// </summary>
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public const string BLANK_LINE = @"\s*\n\s*\n\s*";
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/// <summary>
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/// Tokenize a string on whitespace (space, tab, newline).
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/// In general, users should use the string ``split()`` method instead.
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/// options.IsGap = true
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/// </summary>
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public const string WHITE_SPACE = @"\s+";
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private Regex _regex;
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public List<Token> Tokenize(string sentence, TokenizationOptions options)
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{
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string pattern = options.Pattern;
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if (options.SpecialWords != null)
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{
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options.SpecialWords.ForEach(r =>
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{
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sentence = Regex.Replace(sentence, r, " " + r);
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});
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pattern = String.Join("|", options.SpecialWords) + "|" + pattern;
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}
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_regex = new Regex(pattern);
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var matches = _regex.Matches(sentence).Cast<Match>().ToArray();
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options.IsGap = new string[] { WHITE_SPACE, BLANK_LINE }.Contains(pattern);
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if (options.IsGap)
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{
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int pos = 0;
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var tokens = new Token[matches.Length + 1];
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for (int span = 0; span <= matches.Length; span++)
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{
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var token = new Token
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{
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Text = (span == matches.Length) ? sentence.Substring(pos) : sentence.Substring(pos, matches[span].Index - pos),
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Start = pos
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};
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token.Text = token.Text.Trim();
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tokens[span] = token;
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if (span < matches.Length)
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{
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pos = matches[span].Index + 1;
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}
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}
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return tokens.ToList();
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}
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else
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{
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var m = matches.Select(x => new Token
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{
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Text = x.Value,
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Start = x.Index
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}).ToList();
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if(options.SpecialWords != null)
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{
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int offset = 0;
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m.ForEach(t =>
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{
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if (options.SpecialWords.Contains(t.Text))
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{
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offset++;
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}
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t.Start = t.Start - offset;
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});
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}
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return m;
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}
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}
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}
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}
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