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+; utils
+
+(let! println! (\![x]
+    (print! (fmt "{0}\n" [x]))))
+
+; pure vs. impure demo
+
+; this is a pure function
+(let! f (\[x] x))
+
+(f 10) ; works
+
+; this is an impure function
+(let! g! (\![x] (println! x)))
+
+(g! "foo") ; works
+
+; this is a pure function that tries to call an impure function
+(let! h (\[x] (g! x)))
+
+(h "bar")
+; error: cannot call impure function in pure context
+;   when calling function g! at examples/purity-test.milch:19:15
+;   in a function definition at examples/purity-test.milch:19:12
+;   when calling function h at examples/purity-test.milch:21:1