[Rd] bug with mapply() on an S4 object
Cook, Malcolm
MEC at stowers.org
Wed Nov 28 14:47:37 CET 2012
Yes, yes, excellent and great , I am tracking this development with great interest.
Am I correct that the implications for BioConductor is the tearing out of the Xapply from generics and the expecations that List and descendents would now "just work" with {t,mc,mcl,...}apply? That would be a grand outcome.
~malcolm_cook at stowers.org
>>>>> Hervé Pagès <hpages at fhcrc.org>
>>>>> on Tue, 27 Nov 2012 17:03:05 -0800 writes:
> Some formatting issues when copy/pasting the patch in the
> body of the email so I've attached the diff file.
Thank you, Hervé.
I have committed (a slightly simplified version of) your patch
to R-devel (to become 2.16.0).
Backporting to '2.15.2 patched' would be a bit of work
-- mapply's C interface is not .Internal() there --
so I've kept it in R-devel.
> On 11/27/2012 04:56 PM, Hervé Pagès wrote:
>> 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 at 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)
[.............]
>> 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? */
indeed, there is a more direct way:
tmp2 = lang1(tmp1)
and that's what I've used in the commit.
>> + 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!
Many thanks to you, Hervé!
Martin
>> 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 at 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 at 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: hpages at fhcrc.org
> Phone: (206) 667-5791
> Fax: (206) 667-1319
> [DELETED ATTACHMENT external: mapply.diff, text/x-patch]
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