Version 5.0 The LEDA User Manual

7.6 Persistent Dictionaries ( p dictionary )
1. Definition
An instance D of the parameterized data type p dictionary is a set of items (type
p dic item). Every item in D contains a key from the linearly ordered data type K, called
the key type of D, and an information from data type I, called the information type of D.
If K is a user-defined type, you have to provide a compare function (see Section 2.3).The
number of items in D is called the size of D. A dictionary of size zero is called empty. We
use 〈k, i〉 to denote an item with key k and information i (i is said to be the information
associated with key k). For each k ∈ K there is at most one item 〈k, i〉 ∈ D.
The difference between dictionaries (cf. section 7.1) and persistent dictionaries lies in the
fact that update operations performed on a persistent dictionary D do not change D but
create and return a new dictionary D ′ . For example, D.del(k) returns the dictionary D ′
containing all items it of D with key(it) ≠ k. Also, an assignment D1 = D2 does not
assign a copy of D2 (with new items) to D1 but the value of D2 itself.
#include < LEDA/core/p dictionary.h >
2. Creation
p dictionary D;
creates an instance D of type p dictionary and initializes D
to an empty persistent dictionary.
3. Operations
K D.key(p dic item it) returns the key of item it.
Precondition: it ∈ D.
I D.inf(p dic item it) returns the information of item it.
Precondition: it ∈ D.
p dic item D.locate(const K& k)
returns the item with key k (nil if no such item
exists in D).
p dictionary D.del(const K& k) returns {x ∈ D| key(x) ≠ k}.
p dictionary
D.del item(p dic item it)
returns {x ∈ D| x ≠ it}.
p dictionary D.insert(const K& k, const I& i)
returns D.del(k) ∪ {〈k, i〉}.