Hi, Here is a patch for this (against current R-devel). The "caching" of the .Primitive for 'length' is taken from seq_along() C code (in R-devel/src/main/seq.c).
hpages@thinkpad:~/svn/R$ svn diff R-devel Index: R-devel/src/main/mapply.c =================================================================== --- R-devel/src/main/mapply.c (revision 61172) +++ R-devel/src/main/mapply.c (working copy) @@ -32,14 +32,39 @@ int i, j, m, named, zero = 0; R_xlen_t *lengths, *counters, longest = 0; SEXP vnames, fcall = R_NilValue, mindex, nindex, tmp1, tmp2, ans; + static SEXP length_op = NULL; + /* Store the .Primitive for 'length' for DispatchOrEval to use. */ + if (length_op == NULL) { + SEXP R_lengthSymbol = install("length"); + length_op = eval(R_lengthSymbol, R_BaseEnv); + if (TYPEOF(length_op) != BUILTINSXP) { + length_op = NULL; + error("'length' is not a BUILTIN"); + } + R_PreserveObject(length_op); + } + m = length(varyingArgs); vnames = PROTECT(getAttrib(varyingArgs, R_NamesSymbol)); named = vnames != R_NilValue; lengths = (R_xlen_t *) R_alloc(m, sizeof(R_xlen_t)); for(i = 0; i < m; i++){ - lengths[i] = xlength(VECTOR_ELT(varyingArgs, i)); + int dispatch_ok = 0; + tmp1 = VECTOR_ELT(varyingArgs, i); + if (isObject(tmp1)) { + /* Looks like DispatchOrEval() needs a pairlist. We reproduce what + pairlist(tmp1) would do i.e. tmp2 <- as.pairlist(list(tmp1)). + Is there a more direct way to go from tmp1 to tmp2? */ + PROTECT(tmp2 = allocVector(VECSXP, 1)); + SET_VECTOR_ELT(tmp2, 0, tmp1); + PROTECT(tmp2 = coerceVector(tmp2, LISTSXP)); + dispatch_ok = DispatchOrEval(call, length_op, "length", + tmp2, rho, &ans, 0, 1); + UNPROTECT(2); + } + lengths[i] = dispatch_ok ? asInteger(ans) : xlength(tmp1); if(lengths[i] == 0) zero++; if (lengths[i] > longest) longest = lengths[i]; } Hopefully the bug can be fixed. Thanks! H. On 11/14/2012 09:42 PM, Hervé Pagès wrote:
Hi, Starting with ordinary vectors, so we know what to expect: > mapply(function(x, y) {x * y}, 101:106, rep(1:3, 2)) [1] 101 204 309 104 210 318 > mapply(function(x, y) {x * y}, 101:106, 1:3) [1] 101 204 309 104 210 318 Now with an S4 object: setClass("A", representation(aa="integer")) a <- new("A", aa=101:106) > length(a) [1] 1 Implementing length(): setMethod("length", "A", function(x) length(x@aa)) Testing length(): > length(a) # sanity check [1] 6 No [[ yet for those objects so the following error is expected: > mapply(function(x, y) {x * y}, a, rep(1:3, 2)) Error in dots[[1L]][[1L]] : this S4 class is not subsettable Implementing [[: setMethod("[[", "A", function(x, i, j, ...) x@aa[[i]]) Testing [[: > a[[1]] [1] 101 > a[[5]] [1] 105 Trying mapply again: > mapply(function(x, y) {x * y}, a, rep(1:3, 2)) [1] 101 202 303 101 202 303 Wrong. It looks like internally a[[1]] is always used instead of a[[i]]. The real problem it seems is that 'a' is treated as if it was of length 1: > mapply(function(x, y) {x * y}, a, 1:3) [1] 101 202 303 > mapply(function(x, y) {x * y}, a, 5) [1] 505 In other words, internal dispatch works for [[ but not for length(). Thanks, H.
-- Hervé Pagès Program in Computational Biology Division of Public Health Sciences Fred Hutchinson Cancer Research Center 1100 Fairview Ave. N, M1-B514 P.O. Box 19024 Seattle, WA 98109-1024 E-mail: hpa...@fhcrc.org Phone: (206) 667-5791 Fax: (206) 667-1319 ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel