clojure-koans/src/koans/macros.clj

42 lines
1.0 KiB
Clojure

(defmacro hello [x]
(str "Hello, " x))
(defmacro infix [form]
(list (second form) (first form) (nth form 2)))
(defmacro infix-better [form]
`(~(second form)
__
__ ))
(defmacro r-infix [form]
(list (second form)
(if (instance? clojure.lang.PersistentList (first form))
`(r-infix ~(first form))
(first form))
(if (instance? clojure.lang.PersistentList (nth form 2))
`(r-infix ~(nth form 2))
(nth form 2))
))
(meditations
"Macros are like functions created at compile time"
(= __ (hello "Macros!"))
"Can I haz some infix?"
(= __ (infix (9 + 1)))
"Remember, these are nothing but code transformations"
(= __ (macroexpand '(infix (9 + 1))))
"You can do better than that, hand crafting ftw!"
(= __ (macroexpand '(infix-better (10 * 2))))
"Things dont always work as you would like them to... "
(= __ (macroexpand '(infix-better ( 10 + (2 * 3)))))
"Really, you dont understand recursion until you understand recursion"
(= __ (r-infix (10 + (2 * 3)))))