New linked list

[Sean Kelly]

Derek Parnell wrote:
> On Fri, 12 May 2006 02:52:10 +1000, Walter Bright 
> <newshound at digitalmars.com> wrote:
> 
>> Sean Kelly wrote:
>>> Very cool.  One thing... does this work:
>>>      foreach( Person p; per.each )
>>>     {
>>>         if( p.age > 50 )
>>>             p.listRemove();
>>>     }
>>>  ie. can you remove elements within a foreach?
>>
>> It's undefined behavior. foreach is entitled to assume that the 
>> aggregate is a loop invariant, although the contents of the 
>> aggregate's elements can change. This precludes things like resizing 
>> an array inside a foreach, etc.
> 
> I fell for this one just yesterday. I had ...
> 
>      foreach( Person p; People)
>      {
>          Foo();
>          SomeFunc(); // Potentially adds an item to the People list.
>      }
> 
> but the new items were never processed by Foo() !

If People is a dynamic array and adding a person to the list results in 
a reallocation then I'd expect this.  I would actually consider this 
undefined behavior for dynamic arrays because whether a reallocation 
occurs is implementation defined.  But for a linked list it should work, 
darnit :-)


Sean