[R] evaluation revisited

[Gabor Grothendieck]

On Wed, Jan 28, 2009 at 6:26 AM, Wacek Kusnierczyk
<Waclaw.Marcin.Kusnierczyk at idi.ntnu.no> wrote:
> Gabor Grothendieck wrote:
>> The argument to eval.parent is evaluated before eval.parent
>> ever sees it.
>
> really?  eval.parent is just a regular r function, a wrapper for eval
> with envir=parent.frame().  the arguments to eval.parent are passed to
> eval *unevaluated* (as promises), and are only evaluated when eval needs
> them.  here's a modified eval.parent:

Yes, you're right about the mechanism although quoting the
help page its nevertheless true that it:
"evaluates its first argument in the current scope before
passing it to the evaluator"