What is cond in Lisp?

COND. COND is an unusual function which may take any arbitrary number of arguments. Each argument is called a clause, and consists of a list of exactly two S-expressions. We will call the first S-expression in a clause a condition, and the second S-expression a result.

How cond works in Lisp?

The cond construct in LISP is most commonly used to permit branching. Each clause within the cond statement consists of a conditional test and an action to be performed. If none of the test conditions are evaluated to be true, then the cond statement returns nil.

How do you write if statements in Lisp?

The if macro is followed by a test clause that evaluates to t or nil. If the test clause is evaluated to the t, then the action following the test clause is executed. If it is nil, then the next clause is evaluated.

What does cons do in Lisp?

cons constructs memory objects which hold two values or pointers to values. These objects are referred to as (cons) cells, conses, non-atomic s-expressions (“NATSes”), or (cons) pairs. In Lisp jargon, the expression “to cons x onto y” means to construct a new object with (cons x y) .

What does t mean in Lisp?

LISP uses the self-evaluating symbol nil to mean false. Anything other than nil means true. Unless we have a reason not to, we usually use the self-evaluating symbol t to stand for true.

What is lambda in Lisp?

A lambda expression is a function object written in Lisp. Here is an example: (lambda (x) “Return the hyperbolic cosine of X.” (* 0.5 (+ (exp x) (exp (- x))))) In Emacs Lisp, such a list is a valid expression which evaluates to a function object. A lambda expression, by itself, has no name; it is an anonymous function.

How do I return a Lisp?

Remember, Lisp returns the value of whatever expr was last executed in a function as its value. If n==0 , the above returns 0. If n > 0 , it returns the result of the + expr.

Does Lisp use linked list?

Present day’s Common LISP provides other data structures like, vector, hash table, classes or structures. Lists are single linked lists. In LISP, lists are constructed as a chain of a simple record structure named cons linked together.

What is set in Lisp?

However, it provides number of functions that allows set operations to be performed on a list. You can add, remove, and search for items in a list, based on various criteria. You can also perform various set operations like: union, intersection, and set difference.

When to use cond or if in AutoLISP?

The above example would not be very logical if it were forced into a COND statement. As we can see there are times when only an IF statement will do the trick nicely, and other times when only COND will. The problem is when AutoLISP programmers attempt deal with every conditional logic by the IF function.

How to set a variable in Autodesk AutoLISP?

The following function call sets variable ato 5.0: (setq a 5.0)5.0 Whenever ais evaluated, it returns the real number 5.0. The following command sets two variables, band c: (setq b 123 c 4.7)4.7 setqreturns the value of the last variable set.

What do you need to know about AutoLISP quick start?

All AutoLisp programs must contain the suffix “.LSP” otherwise AutoCAD will not access them when loading. (eg. CHTEXT.LSP). Use a simple text processor such as Notepad to create and edit your lisp files. Is a pre-defined set of instructions that describes a set of actions that AutoLisp is to perform, divided into three sections:

Which is the primary assignment command in AutoLISP?

(setq) is an assignment command, eg : it assigns the value of one variable or constant to another variable. Note: (setq) is the primary assignment command in AutoLisp. The “=” (equals character) is not used as an assignment in AutoLisp. The equals character is used, but only as a non assignment statement.