Lists for built-in functions that can work without brackets

Question

I just noticed that Exit and Quit can work without brackets i.e. a single

Exit

or

Quit

will quit the kernel. Quite surprising!

This isn't mentioned in the document of them. Is there a list for functions with this feature?

Well, I admit I asked this question mainly to show the discovery above :D

Pi and E and EulerGamma though you could argue these are constants (and boringly return themselves). I'd look for functions that take no arguments, though I can't imagine there are many interesting ones that aren't constants. — , Dec 01 '14 at 16:31
These have been mentioned before and they came as quite a surprise to me. Following standard syntax these should be Exit[] or Quit[]. I suspect that these were included only to reduce the frustration of new users who were entering Exit and not getting the desired effect. I have never looked for additional cases though they may exist. — Mr.Wizard, Dec 01 '14 at 18:29
They work without brackets when it's the only input to the cell, not when they are part of any expression though. Suggesting this is some sort of ancient flow control loophole, I dunno. — swish, Jan 18 '17 at 07:03
I suppose Nothing will not fit your criterion? Tho Nothing and Nothing[] are equivalent, it is handy to be able to do things like Nothing @@ {{1}, {2}} and Nothing @@@ {{1}, {2}}. — J. M.'s missing motivation, Jul 25 '19 at 13:50
@J.M.isaway It fits, please add this as an answer :) . (BTW why do you think it doesn't fit my criterion? ) — xzczd, Jul 25 '19 at 14:36
I got confused by the answer you downvoted, but after some thinking, it is indeed an admissible example; I've put it in now. — J. M.'s missing motivation, Jul 28 '19 at 02:30

score 6 · Answer 1 · answered Jul 28 '19 at 02:28

At the OP's request, I am adding the following:

Nothing is a function with very peculiar behavior:

Nothing === Nothing[] === Nothing[x, y]
   True

This means that

Nothing & /@ {{a}, {b}}

and

Nothing /@ {{a}, {b}}

and

Nothing @@@ {{a}, {b}}

all give {} as the result.

score 5 · Answer 2 · answered Jan 18 '17 at 05:49

5

Just noticed Return can work without brackets when it's inside a dialog:

answered Jan 18 '17 at 05:49

xzczd

score -1 · Answer 3 · answered Jul 25 '19 at 05:22

-1

Here

Could also work without brackets.

answered Jul 25 '19 at 05:22

shelure21

(-1) I'm sorry, but Here is not a function. – xzczd Jul 25 '19 at 05:26
@xzczd what is the definition of a function here? p.s. how about Now? – Kuba Jul 25 '19 at 05:46
@Kuba Perhaps I should say "function relationship" or "Head"? Now is not, either. Both Here and Now are used without [], they're built-in symbols, but not functions. – xzczd Jul 25 '19 at 05:54
Right, fair enough. – Kuba Jul 25 '19 at 05:56
@xzczd Yes, you are right. – shelure21 Jul 25 '19 at 07:28

3 Answers3