ICompare class for a list of struct with generic fields

[Bill McCormick]

Hello,

I have a list of struct's that have generic fields:

public struct Item<T1, T2: IComparable<Ite m<T1, T2>{
private T1 _t1;
private T2 _t2;

public T1 t1 {
get { return _t1; }
}

public T2 t2 {
get { return _priority; }
}

internal Item(T1 at1, T2 at2) {
this._t1 = at1;
this._t2 = at2;
}

public int CompareTo(Item< T1, T2other) {
return Comparer<T2>.De fault.Compare(t his.t2, other.t2);
}
}

My question is how to build an IComparer class. Specifically, in the
following, what must X be so that the compiler will be OK with Y & Z.
Have I run into some language syntax limitation? Maybe an interface is
required?

public class MyCompare<X : IComparer<X>
where X : IComparable<Ite m<Y,Z>{

public Compare(Item<Y, Zitem1, Item<Y,Zitem2) { ... }

public bool Equals(Item<Y, Zitem1, Item<Y, Zitem2) { ... }

public int GetHashCode(Ite m<Y, Zitem) {
}

public class MyList<T1, T2: IEnumerable<Ite m<T1, T2>>, ICloneable {

protected List<Item<T1, T2>myList = new Item<T1, T2>>();

protected IComparer<Item< T1, T2>myComparer = new MyCompare<Item< T1,
T2>>();

...

}


Thanks,

Bill

(This is a repost (under my MSDN account) of an early post; hopefully
this is more clear.)

[Jon Skeet [C# MVP]]

Re: ICompare class for a list of struct with generic fields

On Sep 26, 3:21 pm, Bill McCormick <wpmccorm...@ne wsgroup.nospam>
wrote:

<snip>

My question is how to build an IComparer class. Specifically, in the
following, what must X be so that the compiler will be OK with Y & Z.
Have I run into some language syntax limitation? Maybe an interface is
required?
>
public class MyCompare<X : IComparer<X>
     where X : IComparable<Ite m<Y,Z>{
>
   public Compare(Item<Y, Zitem1, Item<Y,Zitem2) { ... }
>
   public bool Equals(Item<Y, Zitem1, Item<Y, Zitem2) { ... }
>
   public int GetHashCode(Ite m<Y, Zitem) {
>
}

Why do you think you need an X at all? It seems to me that you need Y
and Z as type parameters, but not X:

public class MyComparer<Y, Z: IComparer<Item< Y, Z>>

It's not really clear what you're trying to accomplish though...

Jon

[Bill McCormick]

Re: ICompare class for a list of struct with generic fields

Jon Skeet [C# MVP] wrote:

On Sep 26, 3:21 pm, Bill McCormick <wpmccorm...@ne wsgroup.nospam>
wrote:
>
<snip>
>

>My question is how to build an IComparer class. Specifically, in the
>following, what must X be so that the compiler will be OK with Y & Z.
>Have I run into some language syntax limitation? Maybe an interface is
>required?
>>
>public class MyCompare<X : IComparer<X>
> where X : IComparable<Ite m<Y,Z>{
>>
> public Compare(Item<Y, Zitem1, Item<Y,Zitem2) { ... }
>>
> public bool Equals(Item<Y, Zitem1, Item<Y, Zitem2) { ... }
>>
> public int GetHashCode(Ite m<Y, Zitem) {
>>
>}

>
Why do you think you need an X at all? It seems to me that you need Y
and Z as type parameters, but not X:
>
public class MyComparer<Y, Z: IComparer<Item< Y, Z>>
>
It's not really clear what you're trying to accomplish though...
>
Jon

I'm trying to make a custom comparer for sorting a generic list that
contains struct objects with generic fields. X is more of variable for
my question than a generic. I agree, Y & Z are needed, but how? The
following code ...

public class MyCompare<Y,Z : IComparer<Item< Y,Z>{ ... }


results in the compiler complaining ...

Error 1 Using the generic type 'MyCompare<Y,Z> ' requires '2'
type arguments ...

.... when it tries to compile this:

protected IComparer<Item< T1, T2>myComparer = new MyCompare<Item< T1,
T2>>();

[Jon Skeet [C# MVP]]

Re: ICompare class for a list of struct with generic fields

On Sep 26, 3:59 pm, Bill McCormick <wpmccorm...@ne wsgroup.nospam>
wrote:

I'm trying to make a custom comparer for sorting a generic list that
contains struct objects with generic fields. X is more of variable for
my question than a generic. I agree, Y & Z are needed, but how? The
following code ...
>
public class MyCompare<Y,Z : IComparer<Item< Y,Z>{ ... }
>
results in the compiler complaining ...
>
Error   1       Using the generic type 'MyCompare<Y,Z> ' requires '2'
type arguments  ...
>
... when it tries to compile this:
>
protected IComparer<Item< T1, T2>myComparer = new MyCompare<Item< T1,
T2>>();

Yes - you're trying to create an instance just passing in Item<T1, T2>
when you need to pass in T1 and T2 as type arguments:

protected IComparer<Item< T1, T2>myComparer = new MyCompare<T1,
T2>();

Jon

[Bill McCormick]

Re: ICompare class for a list of struct with generic fields

Jon Skeet [C# MVP] wrote:

On Sep 26, 3:59 pm, Bill McCormick <wpmccorm...@ne wsgroup.nospam>
wrote:

>I'm trying to make a custom comparer for sorting a generic list that
>contains struct objects with generic fields. X is more of variable for
>my question than a generic. I agree, Y & Z are needed, but how? The
>following code ...
>>
>public class MyCompare<Y,Z : IComparer<Item< Y,Z>{ ... }
>>
>results in the compiler complaining ...
>>
>Error 1 Using the generic type 'MyCompare<Y,Z> ' requires '2'
>type arguments ...
>>
>... when it tries to compile this:
>>
>protected IComparer<Item< T1, T2>myComparer = new MyCompare<Item< T1,
>T2>>();

>
Yes - you're trying to create an instance just passing in Item<T1, T2>
when you need to pass in T1 and T2 as type arguments:
>
protected IComparer<Item< T1, T2>myComparer = new MyCompare<T1,
T2>();
>
Jon

Thanks Jon. That did the trick. It was confusing trying to follow the
pattern ...

public class MyCompare<T : IComparer<T{ ... }

public class MyList<T: IEnumerable<T>, ICloneable {

protected List<TmyList = new List<T>();

protected IComparer<TmyCo mparer = new MyCompare<T>();

...

}

.... and trying to substitute Item<T1, T2for <T>.


Bill