Macros

I'm learning macros now. They take a little getting used to, but I've written a couple of them to recreate some control structures from other languages. First is the arithmetic-if from old FORTRAN.

(define-macro arith-if

  (lambda (test-val neg-branch zero-branch pos-branch)

    `(cond ((< ,test-val 0) ,neg-branch)

           ((= ,test-val 0) ,zero-branch)

           ((> ,test-val 0) ,pos-branch))))

Next is a for loop from Pascal or BASIC (without a step option).

(define-macro p-for

  (lambda (counter start limit . body)

    `(let loop ((,counter ,start))

         (when (<= ,counter ,limit)

           ,@body

           (loop (+ ,counter 1))))))