Your task
Create Clojure macros are described below.
applyn
This macro should take three arguments: a function, a value, and a n (an integer count). It should return a form which will apply the function to n copies of the value.
Example use:
=> (applyn str "HA" 5)
HAHAHAHAHA
=> (defn splot [] (println "Splot!") 3)
#'cs340-lab15.core/splot
=> (applyn + (splot) 3)
Splot!
Splot!
Splot!
9
Note that the way that applyn works is subtly different than how a function works. If applyn were a function, each argument would be evaluated exactly once. As you can see from the second example above, the val argument is evaluated n times.
Suggestion: you can use the built-in repeat function to generate a sequence with multiple copies of a specified value. E.g.,
(repeat n val)produces a sequence with n copies of val. Also note that using conj to add an element to a sequence returned by repeat does a prepend, as though the sequence were a list.
unless
This macro is similar to the if special form. Its syntax is
(unless cond if-false if-true)
First, cond should be evaluated. If cond yields a false value, if-false should be evaluated and returned. Otherwise, if-true should be evaluated and returned.
Note that only one of if-false and if-true should be evaluated, not both.
Hint: generate an if form as a result of the macro.
Example use:
=> (unless (< 5 4) "yip" "yap")
yip
=> (unless (< 4 5) "yip" "yap")
yap
=> (defn ned [] (println "I'm Ned!") 44)
#'cs340-lab15.core/ned
=> (defn ted [] (println "I'm Ted!") 55)
#'cs340-lab15.core/ted
=> (unless (< 5 4) (ned) (ted))
I'm Ned!
44
=> (unless (< 4 5) (ned) (ted))
I'm Ted!
55
