Had this annoying bug today where something that seemed perfectly resonable just didn’t work. After much investigation it appears that once again brain damage from Java has managed to over into C#. The problem is illustrated with the following code (You can ignore the Tuple for now):<\/p>\n
\r\npublic struct Tuple < TFirst,TSecond >\r\n{\r\n public TFirst first;\r\n public TSecond second;\r\n\r\n public Tuple(TFirst first, TSecond second)\r\n {\r\n\tthis.first = first;\r\n\tthis.second = second;\r\n }\r\n}\r\n\r\n[...]\r\n\r\nTuple < int,string > t = new Tuple < int,string >(1, \"1\");\r\nTuple < int,string > t2 = new Tuple < int,string >(2, \"2\");\r\n\r\nList < tuple < int,string > > lt = new List < tuple < int,string > >();\r\nlt.Add(t);\r\nlt.Add(t2);\r\n\r\nList < tuple < int,string > > lt2 = new List < tuple < int,string > >();\r\nlt2.Add(t);\r\nlt2.Add(t2);\r\n\r\nSystem.Console.WriteLine(\"eq {0}, == {1}\", lt.Equals(lt2), lt == lt2);<\/pre>\nWhich gives the following result:<\/p>\n
\r\neq False, == False<\/pre>\nOk that was strange, in Python and C++ one doesn’t have to use Equal or anything similar and furthermore == gives the correct result since it compares elements memberwise instead of just checking the reference. I recalled that in Java one has to use Equal on strings, since == just compares references. So I googled around and found an explaination in point in the following link at 6.7<\/a>. Note all the special cases. The best part is the following paragraph: “The implementation of Equals() in System.Object (the one you’ll inherit by default if you write a class) compares identity, i.e. it’s the same as operator==”. Apparently List doesn’t to that, despite their efforts to help<\/a>, great… So we’ll have to do that ourselves:<\/t><\/p>\n\r\npublic static IEnumerable < tuple < T1,T2 > > zip < T1,T2 >\r\n(IEnumerable < T1 > l1, IEnumerable < T2 > l2)\r\n{\r\n IEnumerator < T1 > i1 = l1.GetEnumerator();\r\n IEnumerator < T2 > i2 = l2.GetEnumerator();\r\n\r\n while (i1.MoveNext() && i2.MoveNext())\r\n yield return new Tuple < T1,T2 > (i1.Current, i2.Current);\r\n}\r\n\r\npublic static bool sorted_lists_equal < T > (List < T > l1, List < T > l2)\r\nwhere T:IEquatable < T >\r\n{\r\n if (l1.Count != l2.Count)\r\n return false;\r\n foreach (Tuple < T, T > t in zip < T,T >(l1, l2)) {\r\n if (!t.first.Equals(t.second))\r\n return false;\r\n }\r\n return true;\r\n}<\/pre>\n