If condition with and operator

Question

How to use IF condition with AND operator? I'm getting an error

(princ"Enter a year: ")
(defvar y(read))
(defun leap-year(y)
    (if(and(= 0(mod y 400)(= 0(mod y 4))
       (print"Is a leap year"))
       (print"Is not"))))

(leap-year y)

Answer 1

Note that your code should ideally look like this:

(princ "Enter a year: ")
(finish-output)             ; make sure that output is done

(defvar *year*              ; use the usual naming convention for
                            ;  global variables.
  (let ((*read-eval* nil))  ; don't run code during reading
    (read)))

(defun leap-year-p (y)
  ; your implementation here
  ; return a truth value
  )

(print (if (leap-year-p *year*) "yes" "no"))

Alternatively it also is a good idea to not work on the top-level with function calls and global variables. Write procedures/functions for everything. That way your code automatically is more modular, testable and reusable.

(defun prompt-for-year ()
  (princ "Enter a year: ")
  (finish-output)
  (let ((*read-eval* nil))
    (read)))

(defun leap-year-p (y)
  ; your implementation here
  ; return a truth value
  )

(defun check-leap-year ()
  (print (if (leap-year-p (prompt-for-year))
             "yes"
           "no")))

(check-leap-year)