Re: [Rd] Enlightenment sought and a possible buglet in vector.Rd

From: Berwin A Turlach <berwin_at_maths.uwa.edu.au>
Date: Mon 05 Dec 2005 - 04:05:19 GMT

G'day Brian,

>>>>> "BDR" == Prof Brian Ripley <ripley@stats.ox.ac.uk> writes:

    BDR> On Fri, 2 Dec 2005, Berwin A Turlach wrote: [...]

>> The second behaviour that I cannot explain was produced by code
>> written by somebody else, namely:
    [...]
>> The documentation of function() says that if "the end of a
>> function is reached without calling 'return', the value of the
>> last evaluated expression is returned." And this seems to
>> happen in this case:

    BDR> Yes, but that value can be returned with R_Visible set to 0,     BDR> by calling invisible() _or otherwise_. Thanks for the clarification. I had the sneaking suspicion that something like this was happening, but couldn't find anything in the documentation.

I vaguely remember that S has a mechanism to switch auto-printing on/off via a variable, whose name started with ".", but couldn't find anything in the blue book (by now I found .Auto.print in Suesselbeck and VR "S programming). Since we don't have a license for S-plus anymore, I couldn't check S-Plus and I didn't find anything similar in R. I take it that R handles all this via R_Visible at the C level?

    BDR> R does not print the value of a while() loop. [...] (Look     BDR> up the code of do_while for why.) I can see that in the code of do_while the variable R_Visible is set to zero, but there is no explanation for why this is done. But I guess it is for compatibility reasons with S, since by now I found in various books on the S language that the while() loop returns its value invisible.

Thanks for adding the value section to the help page to clarify this issue in the R documentation.

Cheers,

        Berwin



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https://stat.ethz.ch/mailman/listinfo/r-devel Received on Mon Dec 05 15:09:16 2005

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