[Rd] Multiple Assignment built into the R Interpreter?

[Sebastian Martin Krantz]

Dear R Core,

working on my dynamic factor modelling package, which requires several
subroutines to create and update several system matrices, I come back to
the issue of being annoyed by R not supporting multiple assignment out of
the box like Matlab, Python and julia. e.g. something like

A, C, Q, R = init_matrices(X, Y, Z)

would be a great addition to the language. I know there are several
workarounds such as the %<-% operator in the zeallot package or my own %=%
operator in collapse, but these don't work well for package development as
R CMD Check warns about missing global bindings for the created variables,
e.g. I would have to use

A <- C <- Q <- R <- NULL
.c(A, C, Q, R) %=% init_matrices(X, Y, Z)

in a package, which is simply annoying. Of course the standard way of

init <- init_matrices(X, Y, Z)
 A <- init$A; C <- init$C; Q <- init$Q; R <- init$R
rm(init)

is also super cumbersome compared to Python or Julia. Another reason is of
course performance, even my %=% operator written in C has a non-negligible
performance cost for very tight loops, compared to a solution at the
interpretor level or in a primitive function such as `=`.

So my conclusion at this point is that it is just significantly easier to
implement such codes in Julia, in addition to the greater performance it
offers. There are obvious reasons why I am still coding in R and C, thanks
to the robust API and great ecosystem of packages, but adding this could be
a presumably low-hanging fruit to make my life a bit easier. Several issues
for this have been filed on Stackoverflow, the most popular one (
https://stackoverflow.com/questions/7519790/assign-multiple-new-variables-on-lhs-in-a-single-line)
has been viewed 77 thousand times.

But maybe this has already been discussed here and already decided against.
In that case, a way to browse R-devel archives to find out would be nice.

Best regards,

Sebastian

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