> -----Original Message----- > From: r-devel-boun...@r-project.org > [mailto:r-devel-boun...@r-project.org] On Behalf Of Prof Brian Ripley > Sent: Thursday, April 08, 2010 4:41 AM > To: Berwin A Turlach > Cc: r-devel > Subject: Re: [Rd] LOGICAL arguments in FORTRAN code > > On Thu, 8 Apr 2010, Berwin A Turlach wrote: > > > G'day all, > > > > I just took over maintenance of the quadprog package from > Kurt Hornik > > and noticed that one of the FORTRAN routines has an argument that is > > declared to be a LOGICAL. The R code that calls this routine (via > > the .Fortran interface) passes the argument down wrapped in > a call to > > as.logical(). > > > > This was fine (and as documented) under S-Plus 3.4, for > which this code > > was originally developed. However, as far as I know, in R > objects of > > storage mode logical were always supposed to be passed to FORTRAN > > arguments of type INTEGER; and that is what the current "Writing R > > extension manual states". > > > > Thus, given that the port of quadprog existed for quite some time, I > > am wondering whether it is o.k. to pass R objects with storage mode > > logical into FORTRAN code to arguments declared as LOGICAL? > Or should > > the FORTRAN code be corrected to declare the argument in question as > > INTEGER? > > The second to be safe. This is not a question on the S-PLUS/R side > but on the Fortran side. A Fortran compiler may or may not use the > same storage for integer and logical (and it may depend on compiler > flags, although not on the compilers I just checked, gfortran and > SunStudio f95). S-PLUS ran on only a few platforms and with > specified > compilers.
I agree that avoiding LOGICAL's in arguments to Fortran subroutines is a good idea. Fortran compilers are prone to do weird things when encoding LOGICAL values. E.g., I vaguely recall that Apollo's compiler (c. 1990) encoded .true. as 0 (all zeros) and .false. as -1 (all 1's) and HP's compiler of the same era looked only at the 8th bit from the left (no matter if you had a 1, 2, or 4 byte LOGICAL), 0 was .false. and 1 was .true. S+'s .Fortran() took care of these but you couldn't safely call Fortran code with such arguments from C. Avoid character arguments for similar reasons. Bill Dunlap Spotfire, TIBCO Software wdunlap tibco.com > > > > > Cheers, > > > > Berwin > > > > ______________________________________________ > > R-devel@r-project.org mailing list > > https://stat.ethz.ch/mailman/listinfo/r-devel > > > > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > > ______________________________________________ > R-devel@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-devel > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
