LispVector

Overview

LispVector Information

Defined as: lisp.common.type.Vector

Parent Types: LispArray, Sequence

What is a LispVector?

A LispVector in CLforJava is defined as a LispArray with one dimension. A LispVector's size is represented by a non-negative Fixnum. A fill pointer may be specified as well. LispVector is a subtype of LispArray.

What is a fill pointer?

From the HyperSpec :

fill pointer n. (of a vector) an integer associated with a vector that represents the index above which no elements are active. (A fill pointer is a non-negative integer no larger than the total number of elements in the vector. Not all vectors have fill pointers.)

How is the type LispVector represented in Java?

The LispVector (lisp.common.type.Vector) in CLforJava is implemented using java.util.ArrayList to handle resizing LispVector as well as providing much backend functionality from the Collections framework. The choice of ArrayList? comes from the fact that lisp has many specialized types that should be used for performance, as the ArrayList? is slower, but provides a more generic and feature rich Vector, without reinventing the wheel. See relevant discussions for speed analysis. The fill pointer will be represented by a class called FillPointer? .

How are Vectors created?

The LispVector type (lisp.common.type.Vector) will contain a Factory class and method (newInstance) within it's interface definition. This Factory will determine whether or not to create a LispVector or delegate the creation to a more specific type such as LispString for performance reasons. Possible instantiations include:

public static Vector newInstance(int dimensions, java.lang.Class elementType, Object[] initialContents, boolean adjustable,
                                 java.lang.Integer fillPointer)

public static Vector newInstance(int dimensions, java.lang.Class elementType, T initialElement, boolean adjustable,
                                 java.lang.Integer fillPointer)

public static Vector newInstance(int dimensions, java.lang.Class elementType, boolean adjustable, java.lang.Integer fillPointer,
                                 Array displacedTo, int displacedIndexOffset)

public static Vector newInstance(int dimensions, java.lang.Class elementType, boolean adjustable, java.lang.Integer fillPointer)

Information on the parameters: int dimensions - The number of dimensions (will always be 1)

java.lang.Class elementType - type of the elements that will be in the vector

T initialElement - the type of the first element in the vector

Object[] initialContents - an array of the initial contents that will be placed in the vector

boolean adjustable - Determines if the array can grow and shrink in size

java.lang.Integer fillPointer - Allows for the fill pointer to be arbitrarily placed (as opposed to starting at the first element and moving up)

Array displacedTo - Link to the array in which the vector will be stored (as opposed to its own storage)

int displacedIndexOffset - Unknown at the moment.

How is size reallocation handled with type LispVector?

LispVector size reallocation will be handled by the java native type java.util.ArrayList.

Relevant Discussions

Performance analysis of java types

Relevant Links

HyperSpec Vector

CLtL Vector

BitVector

TypeSystem

Functions

Name	Java Method Signature	Status
vector-pop	public T pop()	Implemented
vector-push	public java.lang.Integer push(T newElement)	Implemented
vector-push-extend	public int pushExtend(T newElement,lisp.common.type.Integer extension);	Implemented
vectorp	instanceof	Implemented
aref	get/set	Implemented
svref	svget/svset	Implemented
make-array	Factory.newInstance (see How are Vectors created)	Implemented
fill-pointer	public FillPointer? getFillPointer();	Implemented

-- NeilLee - 15 Feb 2007