HashTable -- the class of all hash tables

Description

A hash table consists of: a class type, a parent type, and a set of key-value pairs. The keys and values can be anything. The access functions below accept a key and return the corresponding value. For details of the mechanism underlying this, see hashing.

One important feature of hash tables that when the keys are consecutive integers starting at 0, the keys are scanned in the natural order.

There is a subclass of HashTable called MutableHashTable which consists of those hash tables whose entries can be changed.

Access functions:

# -- length, or access to elements
. -- access to elements whose key is a symbol

Query functions:

#? -- check for presence of elements
.? -- check for presence of elements whose key is a symbol

Types of hash table :

CoherentSheaf -- the class of all coherent sheaves
Ideal -- the class of all ideals
ImmutableType -- the class of immutable types
ModuleMap -- the class of all maps between modules
MonoidElement -- the class of all monoid elements
MutableHashTable -- the class of all mutable hash tables
MutableMatrix -- the class of all mutable matrices
OptionTable -- the class of hash tables for optional arguments
ProjectiveHilbertPolynomial -- the class of all Hilbert polynomials
RingMap -- the class of all ring maps
SheafOfRings -- the class of sheaves of rings
Tally -- the class of all tally results

Functions and methods returning a hash table :

applyKeys(HashTable,Function), see applyKeys -- apply a function to each key in a hash table
applyPairs(HashTable,Function), see applyPairs -- apply a function to each pair in a hash table
applyValues(HashTable,Function), see applyValues -- apply a function to each value
hashTable(List), see hashTable -- make a hash table
merge(HashTable,HashTable,Function) -- merge hash tables
new HashTable from List -- make a hash table from a list
select(HashTable,Function) -- select pairs from a hash table
select(ZZ,HashTable,Function) -- select a limited number of pairs from a hash table

Methods that use a hash table :

# HashTable -- length
addHook(HashTable,Thing,Function) -- add a hook function to an object for later processing
all(HashTable,Function) -- whether all key/value pairs in a hash table satisfy a specified condition
any(HashTable,Function) -- whether all key/value pairs in a hash table satisfy a specified condition
HashTable # Thing -- get value from hash table
HashTable #? Thing -- check for value in hash table
indices(HashTable) -- preferred indices of a direct sum
installAssignmentMethod(Symbol,HashTable,Function), see installAssignmentMethod -- install methods assignment to the value of an operator
installAssignmentMethod(Symbol,HashTable,HashTable,Function), see installAssignmentMethod -- install methods assignment to the value of an operator
installAssignmentMethod(Symbol,HashTable,HashTable,Option), see installAssignmentMethod -- install methods assignment to the value of an operator
installAssignmentMethod(Symbol,HashTable,Option), see installAssignmentMethod -- install methods assignment to the value of an operator
keys(HashTable) -- keys used in a hash table
package(HashTable), see package -- get containing package
pairs(HashTable), see pairs -- list the pairs in a hash table
remove(HashTable,Thing), see remove -- remove an entry from a hash table
removeHook(HashTable,Thing,Function) -- remove a hook function from an object
runHooks(HashTable,Thing,Thing) -- run the hook functions stored in an object
scanKeys(HashTable,Function), see scanKeys -- apply a function to each key in a hash table or database
scanPairs(HashTable,Function) -- apply a function to pairs in a hash table
scanValues(HashTable,Function), see scanValues -- apply a function to each value in a hash table
tryHooks(HashTable,Thing,Thing) -- try the hook functions stored in an object
values(HashTable) -- values in a hash table

Fixed objects of class HashTable :

LAYOUT -- relative locations of Macaulay 2 files
operatorAttributes
version -- information about this version of the program

For the programmer

The object HashTable is a type, with ancestor class Thing.