Tuples in C#

One of the new C# 4.0 enhancements is a Tuple class  that interests me as I'm currently trying to learn functional programming with F#.  


If your like me your current production environment is likely to remain in 3.5 framework for some time.  This does not mean that we cannot take advantage of some of these enhancements.  A quick search of tuple in C# brought many examples including:


   1:  public class Tuple<T1, T2> : IEqualityComparer<Tuple<T1, T2>>
   2:  {
   3:          /// <summary>
   4:          /// First item
   5:          /// </summary>
   6:          public T1 First { get; private set; }
   7:   
   8:          /// <summary>
   9:          /// Second item
  10:          /// </summary>
  11:          public T2 Second { get; private set; }
  12:   
  13:          /// <summary>
  14:          /// Constructor
  15:          /// </summary>
  16:          public Tuple(T1 first, T2 second)
  17:          {
  18:              First = first;
  19:              Second = second;
  20:          }
  21:   
  22:          /// <summary>
  23:          /// Creates the specified first.
  24:          /// </summary>
  25:          public static Tuple<T1, T2> Create(T1 first, T2 second)
  26:          {
  27:              return new Tuple<T1, T2>(first, second);
  28:          }
  29:  }


This class makes a good candidate for encapsulating the IDictionary.TryGetValue idiom.  

Given the following:

   1:  var dictionary = new Dictionary<int, string> 
   2:  {                                    {1, "One"},
   3:                                       {2, "Two"},
   4:                                       {3, "Three"},
   5:                                       {4, "Four"},
   6:                                       {5, "Five"}
   7:                                   };
   8:   
   9:  string currentValue;
  10:  var  results = dictionary.TryGetValue(0, out currentValue);






TryGetValue returns bool and the value if true.


Since TryGetValue is the recommended method over ContainsKey to reduce the number of accesses, using Tuples seems a natural way to capture the results of this or any operation that returns multiple values.


Using Tuples and extension methods:

   1:  public static Tuple<bool, T2> TryGetTuple<T1, T2>(this IDictionary<T1, T2> dictionary, T1 key)
   2:  {
   3:      T2 results;
   4:       return dictionary.TryGetValue(key, out results)
   5:           ? Tuple<bool, T2>.Create(true, results)
   6:           : Tuple<bool, T2>.Create(false, default(T2));
   7:  }




We can then test:



   1:  [Test]
   2:  public void TestTryGetTuple()
   3:  {
   4:      var nameValues = new Dictionary<int, string>
   5:                           {
   6:                               {1, "One"},
   7:                               {2, "Two"},
   8:                               {3, "Three"},
   9:                               {4, "Four"},
  10:                               {5, "Five"}
  11:                           };
  12:   
  13:      Assert.IsNotNull(nameValues.TryGetTuple(3).Second);
  14:      Assert.IsTrue(nameValues.TryGetTuple(5).First);
  15:      Assert.IsFalse(nameValues.TryGetTuple(6).First);
  16:   
  17:      for (var i = 0; i <= nameValues.Count; ++i )
  18:          Console.WriteLine(nameValues.TryGetTuple(i).Second ?? "(null)");
  19:  }


Not an out variable in site!


Now if I could just grok monads...

Comments

Post a Comment

Popular posts from this blog

All my days Is this the final moment then that all my days have come to? the days that stretch their listless light to long dark nights in restless sheets with stains and dreams of crowded streets past well worn shops that beckon... preparing a small space for me beside the day old bread, or hanging on a butcher's rack disembowel'd and display'd; I find I am, though, unafraid. It seems I've failed to reckon... to put away these childish things, or would it even matter? you pluck me from the bargain tray and think "I could be fatter!" Would you take me in your home again to serve me on a platter? And would it matter after all to toss my bones so carelessly in an unkempt corner of your attic, toss them with a clatter amid unremember'd debris, watch the dust mites scatter? Or stretch me out across your sink like a ragged dishcloth spent in frantic grips that turn and twist that twist and rinse unclean. the pale kings pass the horsemen's git their silent k...
Read more
In the apple orchard On the dense, fleshy beach a young boy fingers his brazen diaper it drinks the tide water waiting A young woman browns in the burnt sunlight the tide retreats unconcerned even with itself August has started without me trade winds betray their boatsmen choosing instead to move inland By the house on the hill a clothesline full of downside shirts wave a toweling jib in the dancing wind The last time we met the night was drenched in rain you said all we had to do was give the wind our name I wondered if it were true In the apple orchard an old man lingers savoring the gritty gnarled leavings the pickers disregard
Read more