Version 5.0 The LEDA User Manual

7.5 Two-Dimensional Maps ( map2 )
1. Definition
An instance M of the parameterized data type map2 is an injective mapping
from the pairs in I1 × I2, called the index type of M, to the set of variables of data type
E, called the element type of M. I must be a pointer, item, or handle type or the type
int. We use M(i, j) to denote the variable indexed by (i, j) and we use dom(M) to denote
the set of “used indices”. This set is empty at the time of creation and is modified by
map2 accesses.
Related data types are map, d arrays, h arrays, and dictionaries.
#include < LEDA/core/map2.h >
2. Types
map2 :: item
the item type.
map2 :: index type1
the first index type.
map2 :: index type2
the second index type .
map2 :: element type
the element type.
3. Creation
map2 M;
creates an injective function m from I1 × I2 to the set of
unused variables of type E, sets xdef to the default value of
type E (if E has no default value then xdef stays undefined)
and dom(M) to the empty set, and initializes M with m.
map2 M(E x);
creates an injective function m from I1 × I2 to the set of
unused variables of type E, sets xdef to x and dom(M) to
the empty set, and initializes M with m.
4. Operations
E& M(const I1 & i, const I2 & j)
returns the variable M(i).
bool M.defined(const I1& i, const I2 & j)
returns true if i ∈ dom(M) and false otherwise.