[R] Existence of formal arguments.

From: Rolf Turner <r.turner_at_auckland.ac.nz>
Date: Fri, 06 Jun 2008 12:23:39 +1200

I just discovered what seems to me to be a slight funny in respect of formal argument names. If I define a function

        foo <- function(a,b){ ... whatever ...}

then ``inside'' foo() the exists() function will return TRUE from ``exists("a") whether an object named ``a'' exists or not. But get("a") will yield an error ``object "a" not found'' in these circumstances.

I presume there is a reason for specifying that an object named by a formal argument always exists --- but it is mysterious by my standards. Can anyone explain the reason for this behaviour?

This is just idle curiosity --- or my hunger for knowledge, whichever way you want to look at it :-) --- it doesn't really matter.

        cheers,

                Rolf Turner

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