HP Integrity NonStop J-Series - Manual (Page 165)

Click on the banner to return to the user guide home page.
©Copyright 1996 Rogue Wave Software
Virtual Functions Inherited from
RWSequenceable
Collections that inherit from the abstract base class RWSequenceable, which inherits from
RWCollectable, have an innate, meaningful ordering. This section describes the virtual functions
inherited from RWSequenceable which make use of that ordering. For example, the following
virtual functions allow access to the ith item in the collection:
virtual RWCollectable*& at(size_t i);
virtual const RWCollectable* at(size_t i) const;
Remember that the first item in any collection is at position i=0. The compiler chooses which
function to use on the basis of whether or not your collection has been declared const: the second
variant of the function is for const collections, the first for all others. The first variant can also be
used as an lvalue, as in the following example:
RWOrdered od;
od.insert(new RWCollectableInt(0)); // 0
od.insert(new RWCollectableInt(1)); // 0 1
od.insert(new RWCollectableInt(2)); // 0 1 2
delete od(1); // Use variant available for RWOrdered
od.at(1) = new RWCollectableInt(3); // 0 3 2
As you might expect, the operations above are efficient for the class RWOrdered , which is
implemented as a vector, but relatively inefficient for a class implemented as a linked-list,
because the entire list must be traversed to find a particular index.
The following virtual functions return the first or last item in the collection, respectively, or nil if
the collection is empty:
virtual RWCollectable* first() const;
virtual RWCollectable* last() const;
The next virtual function returns the index of the first object that is equal to the argument, or the
special value RW_NPOS if there is no such object:
virtual size_t index(const RWCollectable*) const;
Here's an example of the index function in use. The output shows that the index of the variable