FAQ 7.31 Also read
"What Every Computer Scientist Should Know About Floating-Point Arithmetic", ACM Computing Surveys, 23/1, 5–48, also available via http://docs.sun.com/source/806-3568/ncg_goldberg.html. On Thu, Jul 17, 2008 at 8:47 AM, JS Ubei <[EMAIL PROTECTED]> wrote: > Hi all, > > There is a mistake for wich I need your ligths : > > /////////////////////////////////////// > > I have a small C code : > > SEXP testData() > { > SEXP result; > void * rans; > float * my_data; > int my_data_length; > > my_data_length = 2; > my_data = new float[my_data_length]; > > my_data[0] = 29.958334; > my_data[1] = 29.875; > > PROTECT(result = allocVector(REALSXP, my_data_length)); > rans = (void *)REAL(result); > > for(int i=0; i < my_data_length; i++) ((double *)rans)[i] = > (double)(my_data[i]); > > Rprintf("C value #1 : %f\n", ((double *)rans)[0]); > Rprintf("C value #2 : %f\n", ((double *)rans)[1]); > > delete(my_data); > > UNPROTECT(1); > return(result); > } > /////////////////////////////////////// > > And the R corresponding function : > > testData <- function() > { > result <- .Call("testData", PACKAGE="my_package") > print(paste("R value #1 :", result[1])) > print(paste("R value #2 :", result[2])) > return(result) > } > > /////////////////////////////////////// > And in R console, after compilation : > >> my_result <- testData() > C value #1 : 29.958334 > C value #2 : 29.875000 > [1] "R value #1 : 29.9583339691162" > [1] "R value #2 : 29.875" > >> my_result[1] == 29.958334 > [1] FALSE > > ??? > > How can I do to conserve my values ? > > Regards, > > > > _______________________________________________________________ > e http://mail.yahoo.fr > > ______________________________________________ > R-help@r-project.org mailing list > 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. > -- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem you are trying to solve? ______________________________________________ R-help@r-project.org mailing list 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.
