Created
March 1, 2011 14:10
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Clojure quivalent of ruby's andand. Threads the expr through the forms, short circuiting in case of falsey result
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(defmacro &&> | |
"Clojure quivalent of ruby's andand. Threads the expr through the forms, short circuiting in case of falsey result. | |
Inserts x as the second item in the first form, making a list of it if it is not a | |
list already. If there are more forms, inserts the first form as the | |
second item in second form, etc. | |
example: | |
(let [o {:a 123}] | |
(assert (= 124 (&&> o :a (+ 1)))) | |
(assert (= nil (&&> o :a (+ 1) :c :b))) | |
(assert (= false (&&> false :a (+ 1) :c :b))) | |
(assert (= nil (&&> nil :a (+ 1) :c :b))) | |
) | |
" | |
([x] x) | |
([x form] | |
(let [result-sym (gensym "result-sym-")] | |
`(let [~result-sym ~x] | |
(if ~result-sym | |
~(if (seq? form) | |
(concat (list (first form)) (list result-sym) (next form)) | |
(list form result-sym) | |
) | |
~result-sym | |
))) | |
) | |
([x form & more] `(&&> (&&> ~x ~form) ~@more))) |
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