return types

Question

is this type of thing ok.

namespace myclass
{
        class set
        {
        List<object> mList
        //constructors and stuff

        public set union(set passedSet)
        {
                set tempSet = new set();
                        //do stuff
                return tempSet;
        }

        }

}

Basically I have a class library and the methods in that library need to return the type that the class its self is building. Is that ok. When I worte it the word set turned light blue - so I though every thing cool. Now that im using the class library the words set have tured black and im getting data type eror when values are passes to methods etc.

Vulpes · Answer

Richard If I were you I wouldn't use 'set' as the name of a public class. This is because it's a contextual keyword when used within a property declaration and could therefore lead to confusion amongst users of your library. If you must use it then use the title-case 'Set' instead. John No problem :)

Vulpes · Answer

There's also the HashSet class ( http://msdn.microsoft.com/en-us/library/bb359438.aspx ) where you're not bothered about ordering and the SortedSet class ( http://msdn.microsoft.com/en-us/library/dd412070.aspx ) where you are. Both of these have UnionWith IntersectWith ExceptWith and SymmetricExceptWith methods built in silently ignore attempts to add duplicates and are lightning fast in operation.

Andrew Fenster · Answer

There may already be an existing collection class that will do what you're trying to do. For example List has Union() and AddRange() and a variety of other commands. Most IEnumberable classes do.

John Mieske · Answer

One of the errors I saw was this... List mList //constructors and stuff it needed the semi-colon List mList; //constructors and stuff This solved one of my errors. @ Vulpes Thanks for the heads up. I been coding all day.. I cannot believe I missed that.. lol

Vulpes · Answer

John If you don't override it the ToString() method which all classes inherit from System.Object displays the fully qualified name of the class i.e. myclass.set in this example. Console.WriteLine() automatically applies the ToString() method to its argument if you don't call it explicitly.

Sam Hobbs · Answer

The following works. So I don't know why you are gettin an error. Probably the answer is simple and you are expecting it to be more complicated. I think that you will benefit from articles and books about the language. Whatever you are trying to do there is probably articles and books with many more details to help. The hard part is finding the correct terminology to describe what you are doing. using System; namespace _121172 { class set { public set(string comment) { Console.WriteLine(comment); } public set union() { set tempSet = new set(union); return tempSet; } } class Program { static void Main(string[] args) { set set1 = new set(initial); set set2 = set1.union(); } } }

John Mieske · Answer

That is actually pretty cool. I didn't realize set would show the class name. using System ; using System . Collections . Generic ; namespace myclass { class set { List object > mList ; //constructors and stuff public set union ( set passedSet ) { set tempSet = new set (); //do stuff Console . WriteLine ( Creating a union ... ); return tempSet ; } } class Test { static void Main () { set s1 = new set (); Console . WriteLine ( s1 ); set s2 = new set (); Console . WriteLine ( s2 ); set s3 = s1 . union ( s2 ); Console . WriteLine ( s3 ); Console . ReadKey (); } } } OUTPUT : myclass.set myclass.set Creating a union ... myclass.set mList shows not being used.. but other then that it works.

Vulpes · Answer

Although it looks as though it may be circular in fact there's nothing wrong with it and this compiles and runs fine: using System; using System.Collections.Generic; namespace myclass { class set { List mList; //constructors and stuff public set union(set passedSet) { set tempSet = new set(); //do stuff Console.WriteLine(Creating a union ...); return tempSet; } } class Test { static void Main() { set s1 = new set(); set s2 = new set(); set s3 = s1.union(s2); } } } Any error you're getting must therefore be caused by something else. Notice in particular that the set class should be declared to be public if you want to access it from a client of the dll.

John Mieske · Answer

I had to look at this twice.. stumped me for a second. From what I am seeing your calling this : set tempSet = new set(); INSIDE of the class that its supposed to be for. Your class : class set { public set union(set passedSet) { //do stuff return tempSet; } } you cannot set it up like that. Now if your calling from another class : class Program { set tempSet = new set(); test = tempSet.union(); } then it should work just fine. Keep in mind you have to setup what union is going to return. in other words how you are defining 'test' in this above example.