[llvm-commits] Patch: add contains to ImmutableList

[Nick Lewycky]

Nick Lewycky wrote:
> Rui Paulo wrote:
>> Hi,
>>
>> Attached is a patch to add a contains method to ImmutableList. I need this in the clang Static Analyzer.
>
> Do you really need "this->" here?:
>
> +    for (iterator I = this->begin(), E = this->end(); I != E; ++I) {
>
> Yes the type is templated, but it doesn't have a template base.
>
> Secondly:
>
> +      if (*I == V)
>
> The existing code in ImmutableList does not care at all about how
> T::operator== works, instead assuming that the objects in the list are
> uniqued by address. If that assumption is okay with you, you may want to
> write "if (I ==&V)" instead.

On further reflection, that wouldn't work properly when T=int, for 
example, as the ImmutableList would have an intrusive linked list node 
for the '5' element whose doesn't match the '5' you just passed in (from 
the stack).

Nick

> Finally, are you sure that doing an O(n) scan is OK for your use case?
> I'll take your word for it if it's really the right thing to do, but
> just having this may encourage poor algorithm choices by others.
>
> As an alternative, how about a function which takes a T* and returns the
> ImmutableList<T>::iterator pointing to the right element or the end()
> iterator if it's not a member?
>
> Do you have commit access?
>
> Nick
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