[LLVMdev] Some enhancements to ImmutableSet and FoldingSet

[Ted Kremenek]

On Feb 11, 2009, at 8:14 PM, Ben Laurie wrote:

> On Wed, Feb 11, 2009 at 8:24 PM, Ted Kremenek <kremenek at apple.com>  
> wrote:
>> Actually, neither of these methods are needed for ImmutableSet.
>> ImmutableSet already has an 'isEmpty()' method and I have never  
>> really seen
>> a case where "size()" needs to be explicitly calculated.  If you  
>> need size()
>> itself, however, this seems like a perfectly valid addition.
>
> I need to check for size() == 1 (in order to test whether a range set
> has a single possible value).

Ah.  If that is the case, we can implement a 'isSingleton()' method  
with constant time performance (i.e., check if we have a root, and  
check that the root has no children).  Would that work?