C#/EnumerableReduce.cs

   1 using System;
   2 using System.Collections;
   3 using System.Collections.Generic;
   4
   5 namespace IEnumerableExtras
   6 {
   7     /// <summary>
   8     /// <see cref="IEnumerable{T}"/> reduce extension.
   9     /// </summary>
  10     public static class EnumerableReduce
  11     {
  12         /// <summary>
  13         /// Reduce this instance of <see cref="IEnumerable{TValue}"/> to a single value of
  14         /// type <typeparamref name="TValue"/> using given predicate.
  15         /// </summary>
  16         /// <typeparam name="TValue"></typeparam>
  17         /// <param name="collection"></param>
  18         /// <param name="predicate"></param>
  19         /// <returns></returns>
  20         public static TValue Reduce<TValue>(this IEnumerable collection,
  21                                                Func<TValue, TValue, TValue> predicate)
  22         {
  23             bool first = true;
  24             TValue result = default(TValue);
  25
  26             foreach (TValue value in collection)
  27             {
  28                 if (first)
  29                 {
  30                     result = value;
  31                     first = false;
  32                 }
  33                 else
  34                 {
  35                     result = predicate(result, value);
  36                 }
  37             }
  38
  39             return result;
  40         }
  41
  42         /// <summary>
  43         /// Reduce this instance of <see cref="IEnumerable{TValue}"/> to a single value of
  44         /// type <typeparamref name="TValue"/> using given predicate.
  45         /// </summary>
  46         /// <typeparam name="TValue"></typeparam>
  47         /// <param name="collection"></param>
  48         /// <param name="predicate"></param>
  49         /// <returns></returns>
  50         public static TValue Reduce< TValue >( this IEnumerable<TValue> collection,
  51                                                Func<TValue, TValue, TValue> predicate )
  52         {
  53             bool first = true;
  54             TValue result = default( TValue );
  55
  56             foreach ( TValue value in collection )
  57             {
  58                 if ( first )
  59                 {
  60                     result = value;
  61                     first = false;
  62                 }
  63                 else
  64                 {
  65                     result = predicate( result, value );
  66                 }
  67             }
  68
  69             return result;
  70         }
  71
  72         /// <summary>
  73         /// Reduce this instance of <see cref="IEnumerable{TValue}"/> to a single value of
  74         /// type <typeparamref name="TResult"/> using given predicate and an initial value
  75         /// of type <typeparamref name="TResult"/>.
  76         /// </summary>
  77         /// <typeparam name="TValue"></typeparam>
  78         /// <typeparam name="TResult"></typeparam>
  79         /// <param name="collection"></param>
  80         /// <param name="init"></param>
  81         /// <param name="predicate"></param>
  82         /// <returns></returns>
  83         public static TResult Reduce< TValue, TResult >( this IEnumerable<TValue> collection, TResult init,
  84                                                          Func<TResult, TValue, TResult> predicate )
  85         {
  86             foreach ( TValue value in collection )
  87             {
  88                 init = predicate( init, value );
  89             }
  90
  91             return init;
  92         }
  93     }
  94 }