CLJ-1343 - add some?, if-some, and when-some

Signed-off-by: Stuart Halloway <stu@cognitect.com>

Author: puredanger

src/clj/clojure/core.clj

@@ -501,6 +501,13 @@
    :static true}
   [x] (if x false true))
 
+(defn some?
+  "Returns true if x is not nil, false otherwise."
+  {:tag Boolean
+   :added "1.6"
+   :static true}
+  [x] (not (nil? x)))
+
 (defn str
   "With no args, returns the empty string. With one arg x, returns
   x.toString().  (str nil) returns the empty string. With more than
@@ -1746,6 +1753,43 @@
          (let [~form temp#]
            ~@body)))))
 
+(defmacro if-some
+  "bindings => binding-form test
+
+   If test is not nil, evaluates then with binding-form bound to the
+   value of test, if not, yields else"
+  {:added "1.6"}
+  ([bindings then]
+   `(if-some ~bindings ~then nil))
+  ([bindings then else & oldform]
+   (assert-args
+     (vector? bindings) "a vector for its binding"
+     (nil? oldform) "1 or 2 forms after binding vector"
+     (= 2 (count bindings)) "exactly 2 forms in binding vector")
+   (let [form (bindings 0) tst (bindings 1)]
+     `(let [temp# ~tst]
+        (if (nil? temp#)
+          ~else
+          (let [~form temp#]
+            ~then))))))
+
+(defmacro when-some
+  "bindings => binding-form test
+
+   When test is not nil, evaluates body with binding-form bound to the
+   value of test"
+  {:added "1.6"}
+  [bindings & body]
+  (assert-args
+     (vector? bindings) "a vector for its binding"
+     (= 2 (count bindings)) "exactly 2 forms in binding vector")
+   (let [form (bindings 0) tst (bindings 1)]
+    `(let [temp# ~tst]
+       (if (nil? temp#)
+         nil
+         (let [~form temp#]
+           ~@body)))))
+
 (defn push-thread-bindings
   "WARNING: This is a low-level function. Prefer high-level macros like
   binding where ever possible.

test/clojure/test_clojure/control.clj

@@ -152,6 +152,21 @@
              (exception))
        ))
 
+(deftest test-if-some
+  (are [x y] (= x y)
+       1 (if-some [a 1] a)
+       false (if-some [a false] a)
+       nil (if-some [a nil] (exception))
+       3 (if-some [[a b] [1 2]] (+ a b))
+       1 (if-some [[a b] nil] b 1)
+       1 (if-some [a nil] (exception) 1)))
+
+(deftest test-when-some
+  (are [x y] (= x y)
+       1 (when-some [a 1] a)
+       2 (when-some [[a b] [1 2]] b)
+       false (when-some [a false] a)
+       nil (when-some [a nil] (exception))))
 
 (deftest test-cond
   (are [x y] (= x y)

test/clojure/test_clojure/logic.clj

@@ -203,3 +203,10 @@
       ; Java objects
       (new java.util.Date) ))
 
+(deftest test-some?
+  (are [expected x] (= expected (some? x))
+       false nil
+       true false
+       true 0
+       true "abc"
+       true []))