[kyllo]

You would only want to execute an expression and throw away its value for its side effects.

Useful for IO as there's normally nothing I want to pass the value of a println expression to, evaluating already prints it to stdout. Also useful for mutation, but doing this in Clojure feels wrong since the immutable data structures are among the language's greatest strengths.

[SixSigma]

Do you not care if your output succeeded ?

[kyllo]

It honestly hadn't occurred to me that printing to stdout could fail, or that I'd need to check its return value to ensure it was successful. Can you think of an situation where that might happen? And if so, why doesn't println throw an exception?

On the other hand, a side effect like writing to a file or inserting to a database can easily fail, but those of course throw exceptions.

[klibertp]

Output redirected to a file and file being already closed, for one. Or anyway, stdout being closed midway due to many other possible reasons: this is (probably) why printf returns a number of bytes written or -1, for example: http://www.cplusplus.com/reference/cstdio/printf/

[dllthomas]

The question is whether there's anything that can be done about it. Much of the time, there is! And people overlook it more often than they should. But much of the time there isn't, and in that case it might as well be ignored.