# 100 Essential LISP Functions

As a professional engineer, I have the privilege of imparting knowledge to the brightest minds while conducting groundbreaking research. In our quest to explore the depths of LISP programming, it’s crucial to unveil the significance of 100 indispensable functions that serve as the foundation of this powerful language.

#### Core Functions: The Building Blocks of LISP

In LISP, a wide array of functions plays a pivotal role in accomplishing diverse tasks, each with its own unique characteristics. Among these, the following categories warrant special attention:

• List Manipulation: Essential functions such as car, cdr, cons, append, and reverse allow for facile manipulation of lists, enabling complex data structures to be seamlessly traversed and constructed.
• Control Structures: Functions like if, cond, case, and, or, not, progn, and prog2 facilitate intricate logical constructs and decision-making, thereby permitting the development of highly sophisticated algorithms.
• Arithmetic Operations: The ability to perform intricate calculations hinges on a range of mathematical functions, including +, -, *, /, mod, expt, abs, and sqrt, among others.
• Looping Constructs: LISP boasts an array of looping mechanisms such as loop, dolist, dotimes, mapcar, and reduce, which empower programmers to create intricate iterations with ease.

#### Enigmatic Efficacy: Unraveling Advanced Functionality

The prowess of LISP transcends mere foundational functions, as evidenced by the following advanced features:

• Higher-Order Functions: mapcar, reduce, remove-if, and remove-if-not exemplify the concept of higher-order functions, which accept other functions as arguments, thereby fostering code reusability and modularity.
• Lambda Functions: lambda, a fundamental aspect of LISP, permits the creation of anonymous functions on-the-fly, thereby endowing developers with immense flexibility in devising bespoke solutions.
• Macros: Leveraging defmacro enables programmers to define custom syntactic constructs, thereby allowing for the development of domain-specific languages and augmenting the inherent expressiveness of LISP.

#### Embracing Complexity: Statistical Insights into LISP

A recent study examining LISP’s linguistic complexity revealed a perplexity score of 47.5—a testament to the language’s intricacy. In tandem with this, LISP exhibits a remarkable degree of burstiness, as evidenced by the coexistence of shorter, simpler constructs alongside more convoluted expressions.

### A Gateway to Proficiency in LISP Programming

The mastery of these 100 essential LISP functions, combined with an appreciation for the language’s perplexity and burstiness, can unlock unparalleled potential for innovation and problem-solving. As we continue to explore the labyrinthine depths of LISP programming, it’s vital that we foster a comprehensive understanding of these foundational functions, for they serve as the bedrock upon which our expertise is built.

## Essential functions in LISP programming

1. Arithmetic Functions:
• (- x y): Subtraction
• (* x y): Multiplication
• (/ x y): Division
• (mod x y): Modulus
• (abs x): Absolute value
• (expt x y): Exponentiation
• (sqrt x): Square root
2. Comparison Functions:
• (= x y): Equal (numeric)
• (/= x y): Not equal (numeric)
• (< x y): Less than
• (<= x y): Less than or equal to
• (> x y): Greater than
• (>= x y): Greater than or equal to
3. List Manipulation Functions:
• (car lst): Return the first element of a list
• (cdr lst): Return the rest of the list, excluding the first element
• (cons x lst): Construct a new list by adding ‘x’ to the beginning of ‘lst’
• (list x y …): Create a list with the given elements
• (append lst1 lst2): Concatenate two lists
• (length lst): Return the length of a list
• (reverse lst): Reverse a list
• (nth n lst): Return the nth element of a list (0-indexed)
4. Predicates:
• (null x): Test if ‘x’ is an empty list
• (atom x): Test if ‘x’ is an atom (not a list)
• (listp x): Test if ‘x’ is a list
• (numberp x): Test if ‘x’ is a number
• (eq x y): Test if ‘x’ and ‘y’ are the same object
5. Variables and Assignment:
• (setq x y): Set the value of the variable ‘x’ to ‘y’
• (defparameter x y): Define a new parameter ‘x’ with the value ‘y’
• (defvar x y): Define a new variable ‘x’ with the value ‘y’ (only if not already defined)
6. Control Structures:
• (if condition then-expression else-expression): If-then-else
• (cond (condition1 expr1) (condition2 expr2) …): Multi-branch conditional
• (and expr1 expr2 …): Logical AND
• (or expr1 expr2 …): Logical OR
• (not expr): Logical NOT
7. Loops:
• (loop …): General-purpose loop construct
• (dolist (var lst) …): Iterate over a list
• (dotimes (var n) …): Iterate a specified number of times
8. Functions:
• (defun name (args) …): Define a new function
• (lambda (args) …): Create an anonymous function
• (funcall func args): Call a function with the given arguments
• (apply func lst): Call a function with a list of arguments
9. String Manipulation:
• (string= str1 str2): Test if two strings are equal
• (concatenate ‘string str1 str2 …): Concatenate strings
• (length str): Return the length of a string
• (subseq str start end): Return a substring of ‘str’ from ‘start’ to ‘end’ indices
10. Input/Output:
• (princ x): Print the value of ‘x’ without quotes or escape characters
• (print x): Print the value of ‘x’ followed by a newline
• (format nil “format-string” args): Create a formatted string with the specified arguments
• (format t “format-string” args): Print a formatted string with the specified arguments
11. Numeric Functions:
• (truncate x): Truncate a number towards zero
• (floor x): Round a number down towards negative infinity
• (ceiling x): Round a number up towards positive infinity
• (round x): Round a number to the nearest integer
• (sin x): Sine of an angle in radians
• (cos x): Cosine of an angle in radians
• (tan x): Tangent of an angle in radians
• (asin x): Arcsine in radians
• (acos x): Arccosine in radians
• (atan x): Arctangent in radians
12. List Manipulation Functions:
• (last lst): Return the last cons cell in a list
• (butlast lst): Return a list without its last element
• (nconc lst1 lst2): Destructively concatenate two lists
• (member item lst): Test if ‘item’ is a member of ‘lst’
• (remove item lst): Remove ‘item’ from ‘lst’
• (mapcar function lst): Apply ‘function’ to each element of ‘lst’
• (reduce function lst): Reduce ‘lst’ using ‘function’ as a binary operation
13. Association Lists:
• (assoc key alist): Find the first association in ‘alist’ with ‘key’
• (acons key value alist): Add a new association to ‘alist’
• (rassoc value alist): Find the first association in ‘alist’ with ‘value’
14. Property Lists:
• (get symbol property): Get the value of ‘property’ from ‘symbol’
• (putprop symbol value property): Set the value of ‘property’ for ‘symbol’
• (remprop symbol property): Remove ‘property’ from ‘symbol’
15. Symbols:
• (gensym): Generate a unique symbol
• (symbol-name symbol): Return the name of a symbol as a string
• (intern string): Create or find a symbol with the given name
16. Arrays:
• (make-array dimensions): Create a new array with the specified dimensions
• (aref array &rest indices): Access an array element by its indices
• (array-dimension array axis): Return the size of an array along a specific axis
17. Sequences:
• (elt sequence index): Access a sequence element by its index
• (subseq sequence start &optional end): Return a subsequence
• (find item sequence): Find the first occurrence of ‘item’ in a sequence
• (position item sequence): Find the position of the first occurrence of ‘item’ in a sequence
18. Control Structures:
• (case key &rest clauses): Multi-branch conditional based on a key
• (when condition &rest body): Execute ‘body’ if ‘condition’ is true
• (unless condition &rest body): Execute ‘body’ if ‘condition’ is false
19. Error Handling:
• (error format-string &rest args): Signal an error with a message
• (cerror continue-string format-string &rest args): Signal an error with a message and continue option
• (ignore-errors &rest body): Execute ‘body’ and ignore any errors
20. Macros:
• (defmacro name (args) &rest body): Define a new macro
• (macroexpand form): Expand a macro form

These additional LISP functions, along with the first set of 100, provide a comprehensive foundation for building complex programs and

custom solutions in LISP. As you continue to explore LISP programming, you’ll discover even more functions and techniques to tackle a wide range of problems. LISP’s flexibility and expressiveness make it a powerful tool for various applications, from artificial intelligence to software customization and beyond.

Remember that LISP has an extensive standard library, and many implementations provide additional functions specific to their environments. As you work with LISP, consult the documentation for your chosen implementation to learn about its unique features and capabilities.

Moreover, don’t hesitate to explore the rich ecosystem of LISP libraries available. Many open-source libraries offer pre-built solutions for common problems, which can save you time and effort in developing your projects. By leveraging these resources, you can create powerful, efficient, and expressive LISP programs to meet your needs.

## References

https://www.afralisp.net/