gac/macro-exercises.scm

;;Here are two macro ideas (the derivative idea is going to be too much work at the moment):
;; write a if-not macro that swaps the order of the then and else branches:

(defmacro (if-not fool yes no)
`(if ,fool
  ,no
  ,yes))

(TEST
> (if-not (< 10 11) "no" "yes")
"yes")

;write a nif macro that takes any number of branches, similar to cond, but without parens around the test and subsequent then branch; the last branch should be the else branch:

(def (nif-expand args) (if-let-list ))

(TEST
 > (def (t a b c)
        
(nif a "a" b "b" c "c" "none"))
> (t #f #f #f)
"none"
> (t #f #f #t)
"c"
> (t #t #f #t)
"a"
> (t #t #t #t)
"a"
> (t #f #t #t)
"b")

(defmacro (nif . args)
  `(if-let-list ((,args) (args)))
                "none")

;;- write a var macro that takes a string as its argument, which is the name of the variable it should reference.

(TEST
> (let ((a 10) (b 20))
(+ (var "a") (var "b")))
30)

;; You'll need to use assert* again, as well as string->symbol.

;;  write a for macro that works similar to Python:

(TEST
> (def vals '())
> (for x '(1 4 5 6) (push! vals (* 3 x)))
> vals
(18 15 12 3))

;;Note: use the .for-each method, which takes a list or vector as its first argument and a procedure of one argument as its second argument.