What is C analog of C std pair

Question

I m interested  What is C  s analog of std  pair in C    I found System Web UI Pair class  but I d prefer something template-based   Thank you

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C  has tuples as of version 4 0

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I typically extend the Tuple class into my own generic wrapper as follows   public class Statistic lt T gt    Tuple lt string  T gt        public Statistic string name  T value    base name  value          public string Name   get   return this Item1          public T Value   get   return this Item2          and use it like so   public class StatSummary        public Statistic lt double gt  NetProfit   get  set          public Statistic lt int gt  NumberOfTrades   get  set           public StatSummary double totalNetProfit  int numberOfTrades                    this TotalNetProfit   new Statistic lt double gt   Total Net Profit   totalNetProfit             this NumberOfTrades   new Statistic lt int gt   Number of Trades   numberOfTrades              StatSummary summary   new StatSummary 750 50  30   Console WriteLine  Name      summary NetProfit Name        Value      summary NetProfit Value   Console WriteLine  Name      summary NumberOfTrades Value        Value      summary NumberOfTrades Value

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On order to get the above to work  I needed a pair as the key of a dictionary   I had to add       public override Boolean Equals Object o                Pair lt T  U gt  that   o as Pair lt T  U gt           if  that    null              return false          else             return this First Equals that First   amp  amp  this Second Equals that Second           and once I did that I also added      public override Int32 GetHashCode                 return First GetHashCode     Second GetHashCode            to suppress a compiler warning

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The PowerCollections library  formerly available from Wintellect but now hosted on Codeplex   http   powercollections codeplex com  has a generic Pair structure

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I was asking the same question just now after a quick google I found that There is a pair class in  NET except its in the System Web UI         http   msdn microsoft com en-us library system web ui pair aspx  goodness knows why they put it there instead of the collections framework

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If it s about dictionaries and the like  you re looking for System Collections Generic KeyValuePair lt TKey  TValue gt

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I created a C  implementation of Tuples  which solves the problem generically for between two and five values - here s the blog post  which contains a link to the source

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Since  NET 4 0 you have System Tuple lt T1  T2 gt  class      pair is implicitly typed local variable  method scope  var pair   System Tuple Create  Current century   21

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Some answers seem just wrong     you can t use dictionary how would store the pairs  a b  and  a c   Pairs concept should not be confused with associative look up of key and values lot of the above code seems suspect   Here is my pair class  public class Pair lt X  Y gt        private X  x      private Y  y       public Pair X first  Y second                 x   first           y   second             public X first   get   return  x           public Y second   get   return  y           public override bool Equals object obj                if  obj    null              return false          if  obj    this              return true          Pair lt X  Y gt  other   obj as Pair lt X  Y gt           if  other    null              return false           return                first    null   amp  amp   other first    null                        first    null   amp  amp  first Equals other first                   amp  amp                 second    null   amp  amp   other second    null                        second    null   amp  amp  second Equals other second                public override int GetHashCode                 int hashcode   0          if  first    null              hashcode    first GetHashCode            if  second    null              hashcode    second GetHashCode             return hashcode            Here is some test code    TestClass  public class PairTest        TestMethod      public void pairTest                 string s    abc           Pair lt int  string gt  foo   new Pair lt int  string gt  10  s           Pair lt int  string gt  bar   new Pair lt int  string gt  10  s           Pair lt int  string gt  qux   new Pair lt int  string gt  20  s           Pair lt int  int gt  aaa   new Pair lt int  int gt  10  20            Assert IsTrue 10    foo first           Assert AreEqual s  foo second           Assert AreEqual foo  bar           Assert IsTrue foo GetHashCode      bar GetHashCode             Assert IsFalse foo Equals qux            Assert IsFalse foo Equals null            Assert IsFalse foo Equals aaa             Pair lt string  string gt  s1   new Pair lt string  string gt   a    b            Pair lt string  string gt  s2   new Pair lt string  string gt  null   b            Pair lt string  string gt  s3   new Pair lt string  string gt   a   null           Pair lt string  string gt  s4   new Pair lt string  string gt  null  null           Assert IsFalse s1 Equals s2            Assert IsFalse s1 Equals s3            Assert IsFalse s1 Equals s4            Assert IsFalse s2 Equals s1            Assert IsFalse s3 Equals s1            Assert IsFalse s2 Equals s3            Assert IsFalse s4 Equals s1            Assert IsFalse s1 Equals s4

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Apart from custom class or  Net 4 0 Tuples  since C  7 0 there is a new feature called ValueTuple  which is a struct that can be used in this case  Instead of writing   Tuple lt string  int gt  t   new Tuple lt string  int gt   Hello   4     and access values through t Item1 and t Item2  you can simply do it like that    string message  int count      Hello   4     or even    var message  var count      Hello   4

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I was asking the same question just now after a quick google I found that There is a pair class in  NET except its in the System Web UI         http   msdn microsoft com en-us library system web ui pair aspx  goodness knows why they put it there instead of the collections framework

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System Web UI contained the Pair class because it was used heavily in ASP NET 1 1 as an internal ViewState structure   Update Aug 2017  C  7 0    NET Framework 4 7 provides a syntax to declare a Tuple with named items using the System ValueTuple struct     explicit Item typing  string Message  int SomeNumber  t     Hello   4     or using implicit typing  var t    Message  Hello   SomeNumber 4    Console WriteLine   0   1    t Message  t SomeNumber     see MSDN for more syntax examples    Update Jun 2012  Tuples have been a part of  NET since version 4 0   Here is an earlier article describing inclusion in NET4 0 and support for generics   Tuple lt string  int gt  t   new Tuple lt string  int gt   Hello   4

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Unfortunately  there is none  You can use the System Collections Generic KeyValuePair lt K  V gt  in many situations   Alternatively  you can use anonymous types to handle tuples  at least locally   var x   new   First    x   Second   42      The last alternative is to create an own class

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Tuples are available since  NET4 0 and support generics   Tuple lt string  int gt  t   new Tuple lt string  int gt   Hello   4       In previous versions you can use System Collections Generic KeyValuePair lt K  V gt  or a solution like the following   public class Pair lt T  U gt        public Pair                public Pair T first  U second            this First   first          this Second   second             public T First   get  set        public U Second   get  set         And use it like this   Pair lt String  int gt  pair   new Pair lt String  int gt   test   2   Console WriteLine pair First   Console WriteLine pair Second     This outputs   test 2   Or even this chained pairs   Pair lt Pair lt String  int gt   bool gt  pair   new Pair lt Pair lt String  int gt   bool gt     pair First   new Pair lt String  int gt     pair First First    test   pair First Second   12  pair Second   true   Console WriteLine pair First First   Console WriteLine pair First Second   Console WriteLine pair Second     That outputs   test 12 true

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I created a C  implementation of Tuples  which solves the problem generically for between two and five values - here s the blog post  which contains a link to the source

User · Answer

Depending on what you want to accomplish  you might want to try out KeyValuePair    The fact that you cannot change the key of an entry can of course be rectified by simply replacing the entire entry by a new instance of KeyValuePair

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