Compound Conditional in Lisp

Question

I'm new to lisp and I am simply trying to have two functions called at once if a conditional returns true.

(cond 
  ((equals (first expression) "+")
   (function1 parameter)
   (function2 parameter)))

In the above code, I just want function1 and function2 to be called. Any thoughts?

Answer 1

Yes, progn like this:

(cond 
  ((equals (first expression) "+")
   (progn
     (function1 paramter)
     (function2 parameter))))

cond takes one expression to evaluate if true. In this use progn (with its arguments) is that one expression. progn, subsequently take n expressions and evaluates them.

Answer 2

Common Lisp

• EQUALS does not exist, EQUAL does

• COND already does what you want

COND allows several calls after the test:

(cond ((equal (first expression) "+")
       (do-something ...)
       (do-something-more ...)))

• It is called Lisp, not LISP

• read a Beginner Introduction

• use a Reference