Tools.h++ Class Reference

type. The class T must have:
well-defined copy semantics (T::T(const T&) or equivalent);●
well-defined assignment semantics (T::operator=(const T&) or equivalent);●
well-defined equality semantics (T::operator==(const T&)).●
A user-supplied hashing function for type T must be supplied to the constructor when creating a new
table. If T is a Rogue Wave class, then this requirement is usually trivial because most Rogue Wave
objects know how to return a hashing value. In fact, classes RWCString, RWDate, RWTime, and
RWWString contain static member functions called hash that can be supplied to the constructor as is.
The function must have prototype:
unsigned hFun(const T& a);
and should return a suitable hash value for the object a.
To find an object, it is first hashed to determine in which bucket it occurs. The bucket is then searched
for an object that is equal (as determined by the equality operator) to the candidate.
The initial number of buckets in the table is set by the constructor. There is a default value. If the
number of items in the collection greatly exceeds the number of buckets then efficiency will sag
because each bucket must be searched linearly. The number of buckets can be changed by calling
member function resize(). This is an expensive proposition because not only must all items be copied
into the new buckets, but they must also be rehashed.
If you wish this to be automatically done, then you can subclass from this class and implement your
own special insert() and remove() functions which perform a resize() as necessary.
Persistence
None
Example
#include <rw/tvhasht.h>
#include <rw/cstring.h>
#include <rw/rstream.h>
main() {
RWTValHashTable<RWCString> table(RWCString::hash);
table.insert("Alabama"); // NB: Type conversion occurs
table.insert("Pennsylvania");
table.insert("Oregon");
table.insert("Montana");
cout << "The table " <<
(table.contains("Oregon") ? "does " : "does not ") <<
"contain Oregon\n";