"exit 0;" - or - "exit (0);" ?

[braner]

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While K&R explicitly say that exit() is a function, I commonly see
the parens dropped.  Is that "legal"? Does it work on existing compilers?
And while I am asking:  how's "if (foo) {...}" vs. "if foo {...}" ?
(in the case where "foo" is a variable, say an int used as a flag.)

- Moshe Braner, Cornell Univ.