I was practicing one Clojure tutorial and had to ensure that a for loop was executed so I put a `println` command there, but it did not display messages.

So now I have got the question...

This code prints Tom's name:

```
(ns tutorial.core)
(defn -main []
  (println 'Jane)
  (for [a ['Tom]]
    (println a))
;;    'Kate
)

tutorial.core> (-main)
Jane
Tom
(nil)
tutorial.core> 

```

but this not:

```
(ns tutorial.core)
(defn -main []
  (println 'Jane)
  (for [a ['Tom]]
    (println a))
    'Kate
)

tutorial.core> (-main)
Jane
Kate
tutorial.core>

```

Why? In which cases can we expect that `println` will not print texts?