[Rd] assigning objects from .C/.Call
David James <firstname.lastname@example.org>
Tue, 24 Apr 2001 14:16:21 -0400 (EDT)
In section 4.6.7 of "Writing R Extensions" (Version 1.2.1, 2001-01-15)
the C function defineVar() is described as "... the equivalent
of assign(symbol, value, envir = rho, inherits = FALSE) ..."
I interpreted the above (wrongly) as meaning that defineVar() makes
a copy of its "value" argument into the object whose name is specified
in "symbol" in the "rho" environment (that's how assign() works at the
R/S level). However, this is not exactly how defineVar() appears to work.
In particular, it appears to assign the object in the environment "rho",
but further changes in the C code to the object are reflected in the
"assigned" object in rho (i.e., no actual copy of the object is made).
I can see that the implemented behavior is quite useful, but it's not
exactly equivalent to assign(). Perhaps the documentation should be more
explicit and add a sentence to warn users that the data part of the
object is shared? (The sentence may need to be more precise, though.)
system i686, linux-gnu
David A. James
Statistics Research, Room 2C-253 Phone: (908) 582-3082
Bell Labs, Lucent Technologies Fax: (908) 582-3340
Murray Hill, NJ 09794-0636
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