beagled/Lucene.Net/Search/Scorer.cs

   1 /*
   2  * Copyright 2004 The Apache Software Foundation
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at
   7  *
   8  * http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16 using System;
  17 namespace Lucene.Net.Search
  18 {
  19
  20         /// <summary>Expert: Implements scoring for a class of queries. </summary>
  21         public abstract class Scorer
  22         {
  23                 private Similarity similarity;
  24
  25                 /// <summary>Constructs a Scorer. </summary>
  26                 protected internal Scorer(Similarity similarity)
  27                 {
  28                         this.similarity = similarity;
  29                 }
  30
  31                 /// <summary>Returns the Similarity implementation used by this scorer. </summary>
  32                 public virtual Similarity GetSimilarity()
  33                 {
  34                         return this.similarity;
  35                 }
  36
  37                 /// <summary>Scores all documents and passes them to a collector. </summary>
  38                 public virtual void  Score(HitCollector hc)
  39                 {
  40                         while (Next())
  41                         {
  42                                 hc.Collect(Doc(), Score());
  43                         }
  44                 }
  45
  46                 /// <summary>Advance to the next document matching the query.  Returns true iff there
  47                 /// is another match.
  48                 /// </summary>
  49                 public abstract bool Next();
  50
  51                 /// <summary>Returns the current document number.  Initially invalid, until {@link
  52                 /// #Next()} is called the first time.
  53                 /// </summary>
  54                 public abstract int Doc();
  55
  56                 /// <summary>Returns the score of the current document.  Initially invalid, until
  57                 /// {@link #Next()} is called the first time.
  58                 /// </summary>
  59                 public abstract float Score();
  60
  61                 /// <summary>Skips to the first match beyond the current whose document number is
  62                 /// greater than or equal to <i>target</i>. <p>Returns true iff there is such
  63                 /// a match.  <p>Behaves as if written: <pre>
  64                 /// boolean SkipTo(int target) {
  65                 /// do {
  66                 /// if (!next())
  67                 /// return false;
  68                 /// } while (target > doc());
  69                 /// return true;
  70                 /// }
  71                 /// </pre>
  72                 /// Most implementations are considerably more efficient than that.
  73                 /// </summary>
  74                 public abstract bool SkipTo(int target);
  75
  76                 /// <summary>Returns an explanation of the score for <code>doc</code>. </summary>
  77                 public abstract Explanation Explain(int doc);
  78         }
  79 }