Dispatch mechanism seems to alter object before calling method on it

Hi,

This was quite unexpected:

   setGeneric("foo", function(x) standardGeneric("foo"))

   setMethod("foo", "vector", identity)

   foo(matrix(1:12, ncol=3))
   # [1]  1  2  3  4  5  6  7  8  9 10 11 12

   foo(array(1:24, 4:2))
   # [1]  1  2  3  4  5  6  7  8  9 10 11 12 13 14 15 16 17 18 19 20 21 
22 23 24

If I define a method for array objects, things work as expected though:

   setMethod("foo", "array", identity)

   foo(matrix(1:12, ncol=3))
   #      [,1] [,2] [,3]
   # [1,]    1    5    9
   # [2,]    2    6   10
   # [3,]    3    7   11
   # [4,]    4    8   12

So, luckily, I have a workaround.

But shouldn't the dispatch mechanism stay away from the business of
altering objects before passed to it?

Thanks,
H.

Herv? Pag?s

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 fredhutch.org
Phone:  (206) 667-5791
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