struct DefaultKeyedObjectTraits

DefaultKeyedObjectTraits defines a default implementation of traits used to

manage objects stored in associative containers such as hash-tables and

trees.

At a minimum, a class or a struct which is to be used to define the

traits of a keyed object must define the following public members.

GetKey : A static method which takes a constant reference to an object (the

type of which is infered from PtrType) and returns a KeyType

instance corresponding to the key for an object.

LessThan : A static method which takes two keys (key1 and key2) and returns

true if-and-only-if key1 is considered to be less than key2 for

sorting purposes.

EqualTo : A static method which takes two keys (key1 and key2) and returns

true if-and-only-if key1 is considered to be equal to key2.

Rules for keys:

++ The type of key returned by GetKey must be compatible with the key which

was specified for the container.

++ The key for an object must remain constant for as long as the object is

contained within a container.

++ When comparing keys, comparisons must obey basic transative and

commutative properties. That is to say...

LessThan(A, B) and LessThan(B, C) implies LessThan(A, C)

EqualTo(A, B) and EqualTo(B, C) implies EqualTo(A, C)

EqualTo(A, B) if-and-only-if EqualTo(B, A)

LessThan(A, B) if-and-only-if EqualTo(B, A) or (not LessThan(B, A))

DefaultKeyedObjectTraits is a helper class which allows an object to be

treated as a keyed-object by implementing a const GetKey method which returns

a key of the appropriate type. The key type must be compatible with the

container key type, and must have definitions of the

<

and == operators for

the purpose of generating implementation of LessThan and EqualTo.