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.dun...@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 >most >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 >is >something like > >invisible(return(x)) > >which returns x before making it invisible. The fix for this is to use > >return(invisible(x)) > > >> 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 >it. > >Sometimes it is fine to use return(x), but it shouldn't be used >routinely. > >Duncan Murdoch > >> -- Sent from my phone. Please excuse my brevity. On November 13, 2016 >> 3:47:10 AM PST, Duncan Murdoch <murdoch.dun...@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 >intended >>> >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 >as >>> >the parser is concerned, >>> > >>> >return ((1/sqrt(2*pi*Variance))*exp(-(1/2)*((x - >Mean)^2)/Variance)) >>> > >>> >is basically the same as >>> > >>> >f((1/sqrt(2*pi*Variance))*exp(-(1/2)*((x - Mean)^2)/Variance)) >>> > >>> >Duncan Murdoch ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
