[LLVMdev] Some enhancements to ImmutableSet and FoldingSet

[Nick Lewycky]

Bill Wendling wrote:
> On Wed, Feb 11, 2009 at 10:36 AM, Ben Laurie <benl at google.com> wrote:
>> I needed these for some work I'm doing in clang...
>>
> Yes sir! At least this message was informative. One thing:
> 
> +  int size() const {
> +    int n = 0;
> +    for(iterator i = begin() ; i != end() ; ++n, ++i)
> +      ;

Please only call end() once. We use this pattern a lot in LLVM:

for (iterator i = begin(), e = end(); i != e; ++n, ++i)
   ;

But really I think you should just have:
   return std::distance(begin(), end());

Nick

> +    return n;
> +  }
> +  bool empty() const {
> +    return size() == 0;
> +  }
> 
> empty() here isn't a constant-time method. Can you make it's time
> complexity O(1)?
> 
> -bw
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