The "delete" operator is used to delete key/value pairs from associative arrays. Could it be made possible to overload this, so I can have
delete myList[i];
in a custom list class? (maybe this should be possible for arrays too, inefficient though).
It seems like a special case keyword that could better be used more generally.
Sam

Sam McCall wrote:

> The "delete" operator is used to delete key/value pairs from associative arrays. Could it be made possible to overload this, so I can have
> delete myList[i];
> in a custom list class? (maybe this should be possible for arrays too, inefficient though).
> It seems like a special case keyword that could better be used more generally.
> Sam

You could always use a proxy object.

-- 
-Anderson: http://badmama.com.au/~anderson/

J Anderson wrote:

> Sam McCall wrote:
> 
>> The "delete" operator is used to delete key/value pairs from associative arrays. Could it be made possible to overload this, so I can have
>> delete myList[i];
>> in a custom list class? (maybe this should be possible for arrays too, inefficient though).
>> It seems like a special case keyword that could better be used more generally.
>> Sam
> 
> 
> You could always use a proxy object.
> 
Or just use myList.delete(i). I was just thinking it might be nice for consistency.

Or maybe not, dmd doesn't think much of my coding. I was quite taken aback when this code:
Iterator!(T) it=iterator();
...
if(it is ListIterator!(T))

elicited this error message:
collections.d(129): interface ListIterator has no value

Still puzzling over that one :)
Sam

In article <c0aac3$esq$1@digitaldaemon.com>, Sam McCall says...
>Or just use myList.delete(i). I was just thinking it might be nice for consistency.
>
>Or maybe not, dmd doesn't think much of my coding. I was quite taken
>aback when this code:
>Iterator!(T) it=iterator();
>...
>if(it is ListIterator!(T))
>
>elicited this error message:
>collections.d(129): interface ListIterator has no value
>
>Still puzzling over that one :)
>Sam

I don't remember who told you that, but the 'is' operator is the same as the '==='. If you want to check if 'it' is a ListIterator, do a cast.

-----------------------
Carlos Santander Bernal

Carlos Santander B. wrote:

> I don't remember who told you that, but the 'is' operator is the same as the
> '==='. If you want to check if 'it' is a ListIterator, do a cast.

Oops... I saw someone discussing an is or isa operator (like instanceof), and then i saw "is" in the spec and jumped to conclusions :(
Sam

Sam McCall wrote:

> J Anderson wrote:
>
>> Sam McCall wrote:
>>
>>> The "delete" operator is used to delete key/value pairs from associative arrays. Could it be made possible to overload this, so I can have
>>> delete myList[i];
>>> in a custom list class? (maybe this should be possible for arrays too, inefficient though).
>>> It seems like a special case keyword that could better be used more generally.
>>> Sam
>>
>>
>>
>> You could always use a proxy object.
>>
> Or just use myList.delete(i). I was just thinking it might be nice for consistency.
>
> Or maybe not, dmd doesn't think much of my coding. I was quite taken aback when this code:
> Iterator!(T) it=iterator();
> ....
> if(it is ListIterator!(T))
>
> elicited this error message:
> collections.d(129): interface ListIterator has no value
>
> Still puzzling over that one :)
> Sam


I think it would be a good idea to be able to be able to handle deletes of blocks of objects.  Also, proxy objects are often more work then it's worth.

-- 
-Anderson: http://badmama.com.au/~anderson/

What is a proxy object ?

C
"J Anderson" <REMOVEanderson@badmama.com.au> wrote in message
news:c0c3f0$9vn$1@digitaldaemon.com...
> Sam McCall wrote:
>
> > J Anderson wrote:
> >
> >> Sam McCall wrote:
> >>
> >>> The "delete" operator is used to delete key/value pairs from
> >>> associative arrays. Could it be made possible to overload this, so I
> >>> can have
> >>> delete myList[i];
> >>> in a custom list class? (maybe this should be possible for arrays
> >>> too, inefficient though).
> >>> It seems like a special case keyword that could better be used more
> >>> generally.
> >>> Sam
> >>
> >>
> >>
> >> You could always use a proxy object.
> >>
> > Or just use myList.delete(i). I was just thinking it might be nice for
> > consistency.
> >
> > Or maybe not, dmd doesn't think much of my coding. I was quite taken
> > aback when this code:
> > Iterator!(T) it=iterator();
> > ....
> > if(it is ListIterator!(T))
> >
> > elicited this error message:
> > collections.d(129): interface ListIterator has no value
> >
> > Still puzzling over that one :)
> > Sam
>
>
> I think it would be a good idea to be able to be able to handle deletes of blocks of objects.  Also, proxy objects are often more work then it's worth.
>
> -- 
> -Anderson: http://badmama.com.au/~anderson/

C wrote:

>What is a proxy object ?
>
>C
>  
>
It's an object that is used in the place of another object (kinda like boxing). It's kinda like a object that sits in between operations. However, I assumpted because it works in C++ it would work in D. However as the below example shows it doesn't work.  I don't know if this is a bug or by-design. I'm going to summit it as a bug anyways.

Well in the current example (note code below doesn't work):

import std.c.stdio;

template ListT(T)
{
   class Proxy
   {
       this(List thelist, int i) { list = thelist; index = i;}
       ~this() { list.remove(index); }
             //T get() { return T; }
         private:
       List list;
       int index;
   }
     class List
   {
       T [] List;
             void add(T t) { List ~= t;    }
             void remove(int i)
       {            printf("remove %d\n", i);
           //...
       }
             Proxy opIndex(int i)
       {
           Proxy proxy = new Proxy(this, i);
           return proxy;
       }
   }
}


int main ( char [] [] args )
{
   ListT!(int).List test = new ListT!(int).List();
   test.add(10);
   test.add(20);
   test.add(30);
   delete test[1]; //Doesn't work (C:\Program Files\DIDE\Projects\test66\test66.d(52): 'test.opIndex(1)' is not an lvalue)

   return 1;
}


-- 
-Anderson: http://badmama.com.au/~anderson/