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How can I define a function with no return value. For example, the Notation function from the Notation package seems to have no return value; I am looking to do the same thing for some of my custom functions.

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    $\begingroup$ can it not even return Null? if you end last line in function with ; it returns Null. And Null is like nothing. seems to have no return value did you look at the InputForm of what it returns? Since Null does not print to screen. $\endgroup$ – Nasser May 4 '19 at 19:02
  • $\begingroup$ Is that what happens with Notation? I can call Notation[...] without a semicolon and I do not get an Out box. If there is no way to do it without any return value, I can live with that, but it would be cleaner if I could avoid all return values. $\endgroup$ – Kevin Ausman May 4 '19 at 19:13
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    $\begingroup$ I do not know about using Notation to define functions that is why I asked. But my understanding is that function return last evaluation. So if you put ; at end you'll get a Null as return value. So whatever the last thing in the function is what is returned. (Unless you have an explicit Return[..,Module] in the middle. I do not know how to make a function not even return Null. But may be someone knows... $\endgroup$ – Nasser May 4 '19 at 19:18
  • $\begingroup$ Ok, just tried it, and Null seems to not produce an Out box, so I think indeed this is what my example of Notation seems to do. Thank you for pointing me in the right direction. $\endgroup$ – Kevin Ausman May 4 '19 at 19:33
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@Nasser's response in the comments is correct. Returning Null (using a semicolon in the last statement of the function) gives the behavior I was looking for.

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