Adds more macro examples

examples/macros.slo

@@ -11,12 +11,24 @@
       (eval ['lambda [] ['if test (list-join ['begin] ... [['el]])]]))
     (el)))
 
+(define when
+  (macro (test ...)
+    (eval ['if test (cons 'begin ...)])))
+
+(define unless
+  (macro (test ...)
+    (eval ['if ['not test] (cons 'begin ...)])))
+
+
 (define do-count (lambda (count lam)
   (for-each lam (range count))))
 
 (define x -5)
 (while (< x 5) (display-lines x) (set! x (+ x 1)))
 
+(when (> x 0) (display "X is " x " (which is greater than 0)\n") (display "Yay!\n"))
+(unless (< x 0) (display "X is " x "(which is greater than 0)\n") (display "Yay!\n"))
+
 (do-count 5 (lambda (x) (display-lines (+ x 1))))
 
 (display-lines (let ((a 12)(b 3)) (+ a b)))