[R] Question about expression parser for "return" statement

Jeff Newmiller jdnewmil at dcn.davis.ca.us
Mon Nov 14 18:57:45 CET 2016

Sorry, I missed the operation-after-function call aspect of the OP question.

However, I think my policy of avoiding the return function as much as possible serves as an effective antibugging strategy for this problem, in addition to its other benefits.
Sent from my phone. Please excuse my brevity.

On November 14, 2016 2:12:49 AM PST, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>On 13/11/2016 9:42 PM, Jeff Newmiller wrote:
>> I find your response here inconsistent... either including `return`
>causes a "wasted" function call to occur (same result achieved slower)
>or the parser has an optimization in it to prevent the wasted function
>call (only behaviorally the same).
>I don't understand what you are finding inconsistent.  I wasn't talking
>about wasting anything.  I was just saying that expressions like
>return (a)*b
>are evaluated by calling return(a) first, because return() is a 
>function, and then they'll never get to the multiplication.
>BTW, there don't appear to be many instances of this particular bug in 
>CRAN packages, though I don't have a reliable test for it yet.  The
>common error seems to be using just "return", as mentioned before.  The
>fix for that is to add parens, e.g. "return()".  The next most common
>something like
>which returns x before making it invisible.  The fix for this is to use
>> I carefully avoid using the return function in R. Both because using
>it before the end of a function usually makes the logic harder to
>follow and because I am under the impression that using it at the end
>of the function is a small but pointless waste of CPU cycles. That some
>people might be prone to writing a C-like use of "return;" which causes
>a function object to be returned only increases my aversion to using
>Sometimes it is fine to use return(x), but it shouldn't be used
>Duncan Murdoch
>> -- Sent from my phone. Please excuse my brevity. On November 13, 2016
>> 3:47:10 AM PST, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>>> >On 13/11/2016 12:50 AM, Dave DeBarr wrote:
>>>> >> I've noticed that if I don't include parentheses around the
>>> >return
>>>> >> value for the "return" statement, R will assume the first
>>> >parenthetical
>>>> >> expression is the intended return value ... even if that
>>> >parenthetical
>>>> >> expression is only part of a larger expression.
>>>> >>
>>>> >> Is this intentional?
>>> >
>>> >Yes, return is just a function call that has side effects.  As far
>>> >the parser is concerned,
>>> >
>>> >return ((1/sqrt(2*pi*Variance))*exp(-(1/2)*((x -
>>> >
>>> >is basically the same as
>>> >
>>> >f((1/sqrt(2*pi*Variance))*exp(-(1/2)*((x - Mean)^2)/Variance))
>>> >
>>> >Duncan Murdoch

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