Joris Meys
2011-Nov-18 15:43 UTC
[Rd] round() ignores missing arguments if it is used inside another function where some arguments are missing.
I have stumbled across some behaviour in R that I really can't place,
and that makes coding a bit tricky. I know that I can work around it
when explicitly checking for missing arguments, but still...
I have two functions. I have a first function based on paste
? ? fun1 <- function(x,y){
? ? ? print(missing(y))
? ? ? paste(x,'X',sep=y)
? ? }
If I try this function without specifying `y`, I get the (expected)
error message:
? ? > fun1(letters[1:6])
? ? [1] TRUE
? ? Error in paste(x, "X", sep = y) :
? ? ? argument "y" is missing, with no default
The second one with round :
? ? fun2 <- function(x,y){? ? ? print(missing(y))? ? ? round(x,digits=y)? ? }
If I try this function without specifying `y`, it works unexpectedly
whereas it shouldn't :
? ? > fun2(100.1)? ? [1] TRUE? ? [1] 100
In my view, fun1 should definitely give the error message as well, as
it is not intended to have a default behaviour when y is missing.
Still, the round() function ignores the fact y is missing. Is this by
design, is there a check missing in round, or is something else going
on that I am overlooking?
Cheers
Joris> sessionInfo()
R version 2.14.0 (2011-10-31)
Platform: i386-pc-mingw32/i386 (32-bit)
locale:
[1] LC_COLLATE=English_United Kingdom.1252
[2] LC_CTYPE=English_United Kingdom.1252
[3] LC_MONETARY=English_United Kingdom.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United Kingdom.1252
attached base packages:
[1] stats graphics grDevices utils datasets methods
[7] base
loaded via a namespace (and not attached):
[1] tools_2.14.0
--
Joris Meys
Statistical consultant
Ghent University
Faculty of Bioscience Engineering
Department of Mathematical Modelling, Statistics and Bio-Informatics
tel : +32 9 264 59 87
Joris.Meys at Ugent.be
-------------------------------
Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php
Simon Urbanek
2011-Nov-18 16:09 UTC
[Rd] round() ignores missing arguments if it is used inside another function where some arguments are missing.
On Nov 18, 2011, at 10:43 AM, Joris Meys wrote:> I have stumbled across some behaviour in R that I really can't place, > and that makes coding a bit tricky. I know that I can work around it > when explicitly checking for missing arguments, but still... > I have two functions. I have a first function based on paste > > fun1 <- function(x,y){ > print(missing(y)) > paste(x,'X',sep=y) > } > > If I try this function without specifying `y`, I get the (expected) > error message: > > > fun1(letters[1:6]) > [1] TRUE > Error in paste(x, "X", sep = y) : > argument "y" is missing, with no default > > The second one with round : > fun2 <- function(x,y){ print(missing(y)) round(x,digits=y) } > If I try this function without specifying `y`, it works unexpectedly > whereas it shouldn't : > > fun2(100.1) [1] TRUE [1] 100 > In my view, fun1 should definitely give the error message as well, as > it is not intended to have a default behaviour when y is missing. > Still, the round() function ignores the fact y is missing. Is this by > design, is there a check missing in round, or is something else going > on that I am overlooking? >> roundfunction (x, digits = 0) .Primitive("round") it has a default so it is fine for digits to be missing since it will have value 0 in that case ... Cheers, S> Cheers > Joris >> sessionInfo() > R version 2.14.0 (2011-10-31) > Platform: i386-pc-mingw32/i386 (32-bit) > > locale: > [1] LC_COLLATE=English_United Kingdom.1252 > [2] LC_CTYPE=English_United Kingdom.1252 > [3] LC_MONETARY=English_United Kingdom.1252 > [4] LC_NUMERIC=C > [5] LC_TIME=English_United Kingdom.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods > [7] base > > loaded via a namespace (and not attached): > [1] tools_2.14.0 > > -- > Joris Meys > Statistical consultant > > Ghent University > Faculty of Bioscience Engineering > Department of Mathematical Modelling, Statistics and Bio-Informatics > > tel : +32 9 264 59 87 > Joris.Meys at Ugent.be > ------------------------------- > Disclaimer : http://helpdesk.ugent.be/e-maildisclaimer.php > > ______________________________________________ > R-devel at r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > >
Gavin Simpson
2011-Nov-18 16:10 UTC
[Rd] round() ignores missing arguments if it is used inside another function where some arguments are missing.
On Fri, 2011-11-18 at 16:43 +0100, Joris Meys wrote:> I have stumbled across some behaviour in R that I really can't place, > and that makes coding a bit tricky. I know that I can work around it > when explicitly checking for missing arguments, but still... > I have two functions. I have a first function based on paste > > fun1 <- function(x,y){ > print(missing(y)) > paste(x,'X',sep=y) > } > > If I try this function without specifying `y`, I get the (expected) > error message: > > > fun1(letters[1:6]) > [1] TRUE > Error in paste(x, "X", sep = y) : > argument "y" is missing, with no default > > The second one with round : > fun2 <- function(x,y){ print(missing(y)) round(x,digits=y) } > If I try this function without specifying `y`, it works unexpectedly > whereas it shouldn't : > > fun2(100.1) [1] TRUE [1] 100round() is implemented as:> roundfunction (x, digits = 0) .Primitive("round") using the .Primitive means of calling C code. `?.Primitve` refers you to the R Internals manual, which basically states that how the compiled functions should be called and number of arguments etc is stored in a table. This table is given here: http://svn.r-project.org/R/trunk/src/main/names.c The relevant part of which is: /* printname c-entry offset eval arity pp-kind precedence rightassoc * --------- ------- ------ ---- ----- ------- ---------- ----------*/ .... /* Mathematical Functions */ /* primitives: these are group generic and so need to eval args (possibly internally) */ {"round", do_Math2, 10001, 0, -1, {PP_FUNCALL, PREC_FN, 0}}, the eval column indicates features of how arguments are evaluated and what have you. A value of 0 equates to 000 and the last 0 indicates whether arguments are to be evaluated with 0 indicating no evaluation and 1 evaluation. round is indicated to not evaluate its arguments. I don't follow the C code well enough to know if it should be catching the missing argument further on - it must be because it is falling back to the default, but the above explains that the not evaluating arguments is intended. G> In my view, fun1 should definitely give the error message as well, as > it is not intended to have a default behaviour when y is missing. > Still, the round() function ignores the fact y is missing. Is this by > design, is there a check missing in round, or is something else going > on that I am overlooking? > > Cheers > Joris > > sessionInfo() > R version 2.14.0 (2011-10-31) > Platform: i386-pc-mingw32/i386 (32-bit) > > locale: > [1] LC_COLLATE=English_United Kingdom.1252 > [2] LC_CTYPE=English_United Kingdom.1252 > [3] LC_MONETARY=English_United Kingdom.1252 > [4] LC_NUMERIC=C > [5] LC_TIME=English_United Kingdom.1252 > > attached base packages: > [1] stats graphics grDevices utils datasets methods > [7] base > > loaded via a namespace (and not attached): > [1] tools_2.14.0 >-- %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~% Dr. Gavin Simpson [t] +44 (0)20 7679 0522 ECRC, UCL Geography, [f] +44 (0)20 7679 0565 Pearson Building, [e] gavin.simpsonATNOSPAMucl.ac.uk Gower Street, London [w] http://www.ucl.ac.uk/~ucfagls/ UK. WC1E 6BT. [w] http://www.freshwaters.org.uk %~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%~%