
- 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 - Basic Syntax
Basic Building Blocks in LISP
LISP programs are made up of three basic building blocks −
atom
list
string
An atom is a number or string of contiguous characters. It includes numbers and special characters.
Following are examples of some valid atoms −
hello-from-tutorials-point name 123008907 *hello* Block#221 abc123
A list is a sequence of atoms and/or other lists enclosed in parentheses.
Following are examples of some valid lists −
( i am a list) (a ( a b c) d e fgh) (father tom ( susan bill joe)) (sun mon tue wed thur fri sat) ( )
A string is a group of characters enclosed in double quotation marks.
Following are examples of some valid strings −
" I am a string" "a ba c d efg #$%^&!" "Please enter the following details :" "Hello from 'Tutorials Point'! "
Adding Comments
The semicolon symbol (;) is used for indicating a comment line.
For Example,
main.lisp
(write-line "Hello World") ; greet the world ; tell them your whereabouts (write-line "I am at 'Tutorials Point'! Learning LISP")
Output
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −
Hello World I am at 'Tutorials Point'! Learning LISP
Some Notable Points before Moving to Next
Following are some of the important points to note −
The basic numeric operations in LISP are +, -, *, and /
LISP represents a function call f(x) as (f x), for example cos(45) is written as cos 45
LISP expressions are case-insensitive, cos 45 or COS 45 are same.
-
LISP tries to evaluate everything, including the arguments of a function. Only three types of elements are constants and always return their own value
Numbers
The letter t, that stands for logical true.
The value nil, that stands for logical false, as well as an empty list.
Little More about LISP Forms
In the previous chapter, we mentioned that the evaluation process of LISP code takes the following steps.
The reader translates the strings of characters to LISP objects or s-expressions.
The evaluator defines syntax of Lisp forms that are built from s-expressions. This second level of evaluation defines a syntax that determines which s-expressions are LISP forms.
Now, a LISP forms could be.
An Atom
An empty or non-list
Any list that has a symbol as its first element
The evaluator works as a function that takes a valid LISP form as an argument and returns a value. This is the reason why we put the LISP expression in parenthesis, because we are sending the entire expression/form to the evaluator as arguments.
Naming Conventions in LISP
Name or symbols can consist of any number of alphanumeric characters other than whitespace, open and closing parentheses, double and single quotes, backslash, comma, colon, semicolon and vertical bar. To use these characters in a name, you need to use escape character (\).
A name can have digits but not entirely made of digits, because then it would be read as a number. Similarly a name can have periods, but can't be made entirely of periods.
Use of Single Quotation Mark
LISP evaluates everything including the function arguments and list members.
At times, we need to take atoms or lists literally and don't want them evaluated or treated as function calls.
To do this, we need to precede the atom or the list with a single quotation mark.
The following example demonstrates this.
Create a file named main.lisp and type the following code into it.
main.lisp
(write-line "single quote used, it inhibits evaluation") (write '(* 2 3)) (write-line " ") (write-line "single quote not used, so expression evaluated") (write (* 2 3))
Output
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −
single quote used, it inhibits evaluation (* 2 3) single quote not used, so expression evaluated 6