RWTValHashMap<K,T,H,EQ,A>
Module: Essential Tools Module Group: STL Extension-based Collection Classes
Does not inherit
- Local Index
- Synopsis
- Description
- Persistence
- Example
- Related Classes
- Public Typedefs
- Public Constructors
- Public Member Operators
- Public Member Functions
- Related Global Operators
Local Index
Members
Non-Members
Synopsis
#include <rw/tvhdict.h> RWTValHashMap<K,T,H,EQ,A> m;
Description
This class maintains a collection of keys, each with an associated item of type T. These pairs are stored according to a hash object of type H. H must provide a const hash function on elements of type K via public member
unsigned long operator()(const K& x) const;
Equivalent keys within the collection will be grouped together based on an equality object of type EQ. EQ must ensure this grouping via public member
bool operator()(const K& x, const K& y) const;
which should return true if x and y are equivalent.
Note: Any two keys that are equivalent must hash to the same value.
RWTValHashMap<K,T,H,EQ,A> will not accept a key that is equivalent to any key already in the collection. (RWTValHashMultiMap<K,T,H,EQ,A> may contain multiple keys that are equivalent to each other.) Equality is based on an equality object and not on the == operator. If your type has an == operator, then you may want to use the templatized equal_to function object provided by the C++ Standard Library; otherwise, you must define your own equality object.
The value type must have operator==() defined. This requirement is imposed by the C++ Standard Library.
Persistence
Isomorphic
Example
#include <iostream>
#include <functional>
#include <rw/tvhdict.h>
#include <rw/cstring.h>
#include <rw/tools/datetime.h>
struct simple_hash
{
unsigned long
operator()(const RWCString& ref) const {
size_t n = ref.length ();
return (unsigned long)(n ? n * size_t (ref [0]) : 0);
}
};
typedef RWTValHashMap<RWCString, RWDateTime, simple_hash,
std::equal_to<RWCString> > RW;
int main()
{
RW birthdays;
birthdays.insertKeyAndValue(
"John",
RWDateTime("April 12, 1975", RWDateTime::setDate)
);
birthdays.insertKeyAndValue("Ivan", RWDateTime("Nov 2, 1980", RWDateTime::setDate));
// Alternative syntax:
birthdays["Susan"] = RWDateTime("June 30, 1955", RWDateTime::setDate);
birthdays["Gene"] = RWDateTime("Jan 5, 1981", RWDateTime::setDate);
// Print a birthday:
std::cout << birthdays["John"].asString('x') << std::endl;
return 0;
}
Program output:
04/12/75
Related Classes
Class RWTValHashMultiMap<K,T,H,EQ,A> offers the same interface to a collection that accepts multiple keys that compare equal to each other.
Class rw_hashmap<K,T,H,EQ,A> is the C++-standard compliant collection that serves as the underlying implementation for this collection.
Public Typedefs
typedef rw_hashmap<K,T,H,EQ,A> container_type; typedef typename container_type::iterator iterator; typedef typename container_type::const_iterator const_iterator; typedef typename container_type::size_type size_type; typedef std::pair <const K,T> value_type; typedef K key_type; typedef T data_type; typedef std::pair <const K,T>& reference; typedef std::pair <const K,T>& const_reference;
Public Constructors
RWTValHashMap<K,T,H,EQ,A>();
Constructs an empty map.
RWTValHashMap<K,T,H,EQ,A>(const rw_hashmap<K,T,H,EQ,A>& m);
Constructs a map by copying all elements of m.
RWTValHashMap<K,T,H,EQ,A> (const H& h, size_type sz = RW_DEFAULT_CAPACITY);
Creates an empty hashed map which uses the hash object h and has an initial capacity of sz.
RWTValHashMap<K,T,H,EQ,A>(const RWTValHashMap<K,T,H,EQ,A>& rwm);
Copy constructor.
RWTValHashMap<K,T,H,EQ,A>(const value_type* first,
const value_type* last);
Constructs a map by copying elements from the array of value_type pairs pointed to by first, up to, but not including, the pair pointed to by last.
Public Member Operators
RWTValHashMap<K,T,H,EQ,A>& operator=(const RWTValHashMap<K,T,H,EQ,A>& m); RWTValHashMap<K,T,H,EQ,A>& operator=(const rw_hashmap<K,T,H,EQ,A>& m);
Destroys all elements of self and replaces them by copying all associations from m.
bool operator==(const RWTValHashMap<K,T,H,EQ,A>& m) const; bool operator==(const rw_hashmap<K,T,H,EQ,A>& m) const;
Returns true if self compares equal to m, otherwise returns false. Two collections are equal if both have the same number of entries, and iterating through both collections produces, in turn, individual pairs that compare equal to each other.
T& operator[](const K& key);
Looks up key and returns a reference to its associated item. If the key is not in the dictionary, then it will be added with an associated item provided by the default constructor for type T.
Public Member Functions
void apply(void (*fn)(const K&, T&, void*),void* d); void apply(void (*fn)(const K&,const T&,void*),void* d) const;
Applies the user-defined function pointed to by fn to every association in the collection. This function must have one of the prototypes:
void yourfun(const K& key, T& a, void* d); void yourfun(const K& key, const T& a,void* d);
Client data may be passed through parameter d.
iterator begin(); const_iterator begin() const;
Returns an iterator positioned at the first pair in self.
size_type capacity() const;
Returns the number of buckets (slots) available in the underlying hash representation. See resize below.
void clear();
Clears the collection by removing all items from self. Each key and its associated item will have its destructor called.
bool contains(const K& key) const;
Returns true if there exists a key j in self that compares equal to key; otherwise returns false.
bool contains(bool (*fn)(const_reference,void*), void* d) const;
Returns true if there exists an association a in self such that the expression ((*fn)(a,d)) is true, otherwise returns false. fn points to a user-defined tester function which must have prototype:
bool yourTester(const_reference a, void* d);
Client data may be passed through parameter d.
iterator end(); const_iterator end() const;
Returns an iterator positioned "just past" the last association in self.
size_type entries() const;
Returns the number of associations in self.
float fillRatio() const;
Returns the ratio entries()/capacity().
bool find(const K& key, K& r) const;
If there exists a key j in self that compares equal to key, assigns j to r and returns true. Otherwise, returns false and leaves the value of r unchanged.
bool
find(bool (*fn)(const_reference,void*),void* d,
pair<K,T>& r) const;
If there exists an association a in self such that the expression ((*fn)(a,d)) is true, assigns a to r and returns true. Otherwise, returns false and leaves the value of k unchanged. fn points to a user-defined tester function which must have prototype:
bool yourTester(const K& a, void* d);
Client data may be passed through parameter d.
bool findValue(const K& key, T& r) const;
If there exists a key j in self that compares equal to key, assigns the item associated with j to r and returns true. Otherwise, returns false and leaves the value of r unchanged.
bool findKeyValue(const K& key, K& kr, T& tr) const;
If there exists a key j in self that compares equal to key, assigns j to kr, assigns the item associated with j to tr, and returns true. Otherwise, returns false and leaves the values of kr and tr unchanged.
bool insert(const K& key, const T& a);
Adds key with associated item a to the collection. Returns true if the insertion is successful, otherwise returns false. The function will return true unless the collection already holds an association with the equivalent key.
bool isEmpty() const;
Returns true if there are no items in the collection, false otherwise.
const K& minElement() const; const K& maxElement() const;
Returns a reference to the minimum or maximum key in the collection. Type K must have well-defined less-than semantics (K::operator<(const K&) or equivalent).
size_type occurrencesOf(const K& key) const;
Returns the number of keys j in self that compare equal to key.
size_type
occurrencesOf(bool (*fn)(const_reference,void*),void* d)
const;
Returns the number of associations a in self such that the expression((*fn)(a,d)) is true. fn points to a user-defined tester function which must have prototype:
bool yourTester(const_reference a, void* d);
Client data may be passed through parameter d.
bool remove(const K& key);
Removes the first association with key j in self such that the expression (j == key) is true and returns true. Returns false if there is no such association.
bool remove(bool (*fn)(const_reference,void*), void* d);
Removes the first association a in self such that the expression ((*fn)(a,d)) is true and returns true. Returns false if there is no such element. fn points to a user-defined tester function which must have prototype:
bool yourTester(const_reference a, void* d);
Client data may be passed through parameter d.
size_type removeAll(const K& key);
Removes all elements j in self that compare equal to key. Returns the number of items removed.
size_type removeAll(bool (*fn)(const_reference,void*), void* d);
Removes all associations a in self such that the expression ((*fn)(a,d))is true. Returns the number of items removed. fn points to a user-defined tester function which must have prototype:
bool yourTester(const_reference a, void* d);
Client data may be passed through parameter d.
void resize(size_type sz);
Changes the capacity of self by creating a new hashed map with a capacity of sz. resize copies every element of self into the new container and finally swaps the internal representation of the new container with the internal representation of self.
rw_hashmap<K,T,H,EQ,A>& std(); const rw_hashmap<K,T,H,EQ,A>& std() const;
Returns a reference to the underlying collection that serves as the implementation for self. This reference may be used freely, providing access to the C++-standard interface as well as interoperability with other software components that make use of the C++-standard compliant collections.
Related Global Operators
RWvostream&
operator<<(RWvostream& strm,
const RWTValHashMap<K,T,H,EQ,A>& coll);
RWFile&
operator<<(RWFile& strm, const
RWTValHashMap<K,T,H,EQ,A>& coll);
Saves the collection coll onto the output stream strm, or a reference to it if it has already been saved.
RWvistream&
operator>>(RWvistream& strm,
RWTValHashMap<K,T,H,EQ,A>& coll);
RWFile&
operator>>(RWFile& strm, RWTValHashMap<K,T,H,EQ,A>& coll);
Restores the contents of the collection coll from the input stream strm.
RWvistream& operator>>(RWvistream& strm, RWTValHashMap<K,T,H,EQ,A>*& p); RWFile& operator>>(RWFile& strm, RWTValHashMap<K,T,H,EQ,A>*& p);
Looks at the next object on the input stream strm and either creates a new collection off the heap and sets p to point to it, or sets p to point to a previously read instance. If a collection is created off the heap, then you are responsible for deleting it.
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