std: Add if? if-not? when? when-not? truey fns

Author: ingydotnet

core/src/ys/std.clj

@@ -723,6 +723,18 @@
 
 (defmacro &&& [x & xs] `(and? ~x ~@xs))
 
+(defn if? [cond then else]
+  (if (truey? cond) then else))
+
+(defn if-not? [cond then else]
+  (if-not (truey? cond) then else))
+
+(defn when? [cond & body]
+  (when (truey? cond) (doall body)))
+
+(defn when-not? [cond & body]
+  (when (falsey? cond) (doall body)))
+
 
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