
- LISP Tutorial
- LISP - Home
- LISP - Overview
- LISP - Environment
- LISP - REPL
- LISP - Program Structure
- LISP - Basic Syntax
- LISP - Data Types
- Lisp Macros
- LISP - Macros
- LISP - Backquote and Comma
- LISP - Code Generation Using Macro
- LISP - Variable Capture and Hygienic macro
- LISP - Scope and Binding
- LISP - Macro Writing Style
- LISP - Macro Characters
- LISP - Read-Time Macros
- LISP - Compiler Macros
- LISP - Uses of Macros
- Lisp Functions
- LISP - Functions
- LISP - Functions vs Macros
- LISP - Calling Function using funcall
- LISP - Calling Function using apply
- LISP - Closures
- LISP - Functions as Arguments
- LISP - Functions as Return Values
- LISP - Recursion
- LISP - Built-in Functions
- Lisp Predicates
- LISP - Predicates
- LISP - Generic Data Type Predicates
- LISP - Specific Data Type Predicates
- LISP - Equality Predicates
- LISP - Numeric Predicates
- LISP - Comparison Predicates
- LISP - Logical Predicates
- LISP - List Predicates
- LISP - Custom Predicates
- LISP - Chaining Predicates
- Lisp Arrays
- LISP - Arrays
- LISP - Adjustable Arrays
- LISP - Fill Pointers in Arrays
- LISP - Specialized Arrays
- LISP - Arrays Properties
- LISP - Iterating over Arrays
- LISP - Multidimensional Arrays
- LISP - Row-Major Order
- Lisp Strings
- LISP - Strings
- LISP - String Concatenation
- LISP - String Comparison
- LISP - String Case Conversion
- LISP - String Trimmimg
- LISP - String Searching
- LISP - Getting Substring
- LISP - String Replacement
- LISP - Sorting Strings
- LISP - Merging Strings
- LISP - Accessing Characters of String
- LISP - String length
- LISP - Escape Sequences
- Lisp Sequences
- LISP - Sequences
- LISP - Accessing Element of Sequence
- LISP - Sequence length
- LISP - Getting Subsequence
- LISP - Search Element in Sequence
- LISP - Sequence Concatenation
- LISP - Reversing a Sequence
- LISP - Mapping Sequence Element
- LISP - position of Element
- LISP - Remove an Element
- LISP - Sort Sequence
- LISP - Merge Sequences
- LISP - every function
- LISP - some function
- LISP - notany function
- LISP - notevery function
- Lisp Lists
- LISP - Lists
- LISP - Accessing Elements of Lists
- LISP - Modifications to Lists
- LISP - Using mapcar on List
- LISP - Using mapc on List
- LISP - Using reduce on List
- LISP - Removing elements from List
- LISP - Reversing a List
- LISP - Sorting a List
- LISP - Searching a List
- LISP - List vs Vectors
- LISP - Matrix Multiplication
- Lisp Vectors
- LISP - Vectors
- LISP - Creating Vectors
- LISP - Accessing Elements of Vectors
- LISP - Modifications to Vectors
- LISP - Adjustable Vectors
- LISP - Specialized Vectors
- LISP - Vector Functions
- Lisp Set
- LISP - Set
- LISP - Adding elements to the Set
- LISP - Getting SubSet from a Set
- LISP - Set Difference
- LISP - Set Exclusive OR
- LISP - Set Intersection
- LISP - Set Union
- LISP - Representing Set with HashTable
- LISP - List as Set vs HashTable as Set
- Lisp Tree
- LISP - Tree
- LISP - Recursive Traversal
- LISP - Inorder Traversal
- LISP - Preorder Traversal
- LISP - Postorder Traversal
- LISP - Depth First Traversal
- LISP - Modifying Tree
- LISP - Search Tree
- LISP - Binary Tree
- Lisp Hash Table
- LISP - Hash Table
- Adding Values to Hash Table
- Removing Values from Hash Table
- Updating Values of Hash Table
- Iterating Hash Table Entries
- Searching key in HashTable
- Checking Size of HashTable
- Using Custom Equality Check
- Lisp - Input − Output
- LISP - Input − Output
- LISP - Streams
- LISP - Reading Data from Streams
- LISP - Writing Data to Streams
- LISP - File I/O
- LISP - String I/O
- LISP - Formatting with Format
- LISP - Interactive I/O
- LISP - Error Handling
- LISP - Binary I/O
- Lisp - Structures
- LISP - Structures
- LISP - Accessors and Mutators
- LISP - Structure Options
- LISP - Structure Types
- LISP - Applications and Best Practices
- Lisp - CLOS
- LISP - CLOS
- Lisp - Objects
- LISP - Class
- LISP - Slots and Accessors
- LISP - Generic Functions
- LISP - Class Precedence
- LISP - Metaobject Protocol
- LISP - Multimethods
- LISP - Multiple Inheritance
- LISP - Method Combinations
- LISP - Method Combinations
- LISP - :before Method Combination
- LISP - :primary Method Combination
- LISP - :after Method Combination
- LISP - :around Method Combination
- LISP - + Method Combination
- LISP - and Method Combination
- LISP - append Method Combination
- LISP Useful Resources
- Lisp - Quick Guide
- Lisp - Useful Resources
- Lisp - Discussion
Lisp - Structures
Structures are one of the user-defined data type, which allows you to combine data items of different kinds.
Structures are used to represent a record. Suppose you want to keep track of your books in a library. You might want to track the following attributes about each book −
- Title
- Author
- Subject
- Book ID
Defining a Structure
The defstruct macro in LISP allows you to define an abstract record structure. The defstruct statement defines a new data type, with more than one member for your program.
To discuss the format of the defstruct macro, let us write the definition of the Book structure. We could define the book structure as −
(defstruct book title author subject book-id )
Please note
The above declaration creates a book structure with four named components. So every book created will be an object of this structure.
It defines four functions named book-title, book-author, book-subject and book-book-id, which will take one argument, a book structure, and will return the fields title, author, subject and book-id of the book object. These functions are called the access functions.
The symbol book becomes a data type and you can check it using the typep predicate.
There will also be an implicit function named book-p, which is a predicate and will be true if its argument is a book and is false otherwise.
Another implicit function named make-book will be created, which is a constructor, which, when invoked, will create a data structure with four components, suitable for use with the access functions.
The #S syntax refers to a structure, and you can use it to read or print instances of a book.
An implicit function named copy-book of one argument is also defined that. It takes a book object and creates another book object, which is a copy of the first one. This function is called the copier function.
You can use setf to alter the components of a book, for example
(setf (book-book-id book3) 100)
Example
Create a new source code file named main.lisp and type the following code in it.
main.lisp
; define a structure book (defstruct book title author subject book-id ) ; create structure using make-book and assign it to book1 ( setq book1 (make-book :title "C Programming" :author "Nuha Ali" :subject "C-Programming Tutorial" :book-id "478") ) ; create structure using make-book and assign it to book2 ( setq book2 (make-book :title "Telecom Billing" :author "Zara Ali" :subject "C-Programming Tutorial" :book-id "501") ) ; print book1 structure (write book1) ; terminate printing (terpri) ; print book2 structure (write book2)
Output
When you execute the code, it returns the following result −
#S(BOOK :TITLE "C Programming" :AUTHOR "Nuha Ali" :SUBJECT "C-Programming Tutorial" :BOOK-ID "478") #S(BOOK :TITLE "Telecom Billing" :AUTHOR "Zara Ali" :SUBJECT "C-Programming Tutorial" :BOOK-ID "501")
Example
Update the source code file named main.lisp and type the following code in it.
main.lisp
; define a structure book (defstruct book title author subject book-id ) ; create and assign a structure to book1 ( setq book1 (make-book :title "C Programming" :author "Nuha Ali" :subject "C-Programming Tutorial" :book-id "478") ) ; print book1 structure (write book1) ; terminate printing (terpri) ; copy book1 to book2 (setq book2( copy-book book1)) ; update the book-id to 100 (setf (book-book-id book2) 100) ; terminate printing (terpri) ; print book2 (write book2)
Output
When you execute the code, it returns the following result −
#S(BOOK :TITLE "C Programming" :AUTHOR "Nuha Ali" :SUBJECT "C-Programming Tutorial" :BOOK-ID "478") #S(BOOK :TITLE "C Programming" :AUTHOR "Nuha Ali" :SUBJECT "C-Programming Tutorial" :BOOK-ID 100)