Macros allow you to extend the syntax of standard LISP.
Technically, a macro is a function that takes an s-expression as arguments and returns a LISP form, which is then evaluated.
In LISP, a named macro is defined using another macro named defmacro. Syntax for defining a macro is −
(defmacro macro-name (parameter-list)) "Optional documentation string." body-form
The macro definition consists of the name of the macro, a parameter list, an optional documentation string, and a body of Lisp expressions that defines the job to be performed by the macro.
Let us write a simple macro named setTo10, which will take a number and set its value to 10.
Create new source code file named main.lisp and type the following code in it.
(defmacro setTo10(num) (setq num 10)(print num)) (setq x 25) (print x) (setTo10 x)
When you click the Execute button, or type Ctrl+E, LISP executes it immediately and the result returned is −