Lisp - List vs Vector

Lisp provides List and Vector as a data structures to store a collection of elements but both structures are having different characteristics and a suitablility varies as per the requirement. Following is the comparison.

List

• Implementation− List is implemented as a single linked list where each node points to the next node.

• Memory Storage− List is stored in non-contigous memory locations.

• Access− List elements are accessed sequentially. List is to be traversed from beginning to access an element.

• Insertion/Deletion− Insertion/Deletion from beginning is highly efficient.

• Use cases− A list is useful when order is important and Insertion/Deletion operations are frequent.

Vector

• Implementation− Vector is implemented as single dimensional array.

• Memory Storage− Vector is stored in contigous memory locations.

• Access− Random Access. Vector elements can be accessed randomly using their indexes.

• Insertion/Deletion− Insertion/Deletion is less efficient as shifting elements may hamper performance.

• Use cases− A vector is useful when random access is important and collection size is fixed.

List vs Vector

Following table summarizes the key differences.

Choosing List or Vector

• List − When we need to maintain order of insertion in a collection and insertion/deletion operations are frequent especially at the beginning of the list.

• Vector − When collection size is fixed and element are to accessed frequently by indexes.

Example - List

Following is an example of a List of numbers.

main.lisp

; define a list
(defvar myList '(1 2 3 4 5))
; print the list
(print myList)

Output

When you execute the code, it returns the following result −

(1 2 3 4 5)

Example - Vector

Following is an example of a vector of numbers.

main.lisp

; define a vector
(defvar myVector #(1 2 3 4 5))
; print the vector
(print myVector)

Output

When you execute the code, it returns the following result −

#(1 2 3 4 5)