58 lines
1.8 KiB
Plaintext
58 lines
1.8 KiB
Plaintext
;;;; A when whose value is kept answers an Option: Some of its body when the
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;;;; test holds, None when it does not. As a statement it answers nothing.
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;;;; Where a dyn is wanted it answers the body or nil, since dyn has no
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;;;; Option. A body that is already an Option is not flattened.
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(defn show [o (Option i32)] ()
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(match o (Some v) (println v) None (println "none")))
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;; Returned: the return type is the want.
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(defn half [n i32] (Option i32) (when (= 0 (% n 2)) (/ n 2)))
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;; Nested, as Rust's bool::then: None from the body stays apart from a
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;; failed test.
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(defn wrap [c bool o (Option i32)] (Option (Option i32)) (when c o))
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(defn level [oo (Option (Option i32))] ()
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(match oo
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(Some o) (match o (Some v) (println v) None (println "some none"))
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None (println "none")))
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;; Dyn: the body or nil.
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(defn dyn-when [x] dyn (when x 5))
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;; A lambda's last form is kept at the return type its position wants.
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(defn call-it [f (Fn [] (Option i32))] () (show (f)))
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;; A kept cond with no :else is a when over several tests.
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(defn pick [n i32] (Option i32) (cond (= n 1) 10 (= n 2) 20))
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(defn dpick [n] dyn (cond (= n 1) "a" (= n 2) "b"))
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(defn main [] ()
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(show (half 10))
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(show (half 7))
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;; A let's value.
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(let [a (when (> 3 2) 42)
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b (when (> 2 3) 42)]
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(show a)
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(show b))
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;; An argument.
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(show (when true 9))
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(level (wrap true (Some 1)))
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(level (wrap true None))
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(level (wrap false (Some 1)))
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(println (dyn-when true))
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(println (dyn-when nil))
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(call-it (fn [] (when true 6)))
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(call-it (fn [] (when false 6)))
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(show (pick 2))
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(show (pick 3))
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(let [k (cond (> 3 5) 1 (> 3 2) 2)] (show k))
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(println (dpick 1))
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(println (dpick 9))
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(cond (> 3 5) (println "no") (> 3 2) (println "cond stmt"))
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;; Statements, unchanged.
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(when true (println "ran"))
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(when false (println "not run"))
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(println "end"))
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