On 13/03/2016 9:54 AM, Henrik Bengtsson wrote:
Just checking in to see whether it is intended or not that assigning
new formals to a function/closure causes any attributes to be dropped:
For srcref, yes. Changing the formals or body of a function would
usually make them invalid.
I think it makes a reasonable default behaviour for other attributes as
well.
Duncan Murdoch
EXAMPLE:
fcn <- structure(function() {}, foo="foo", class=c("foo"))
str(fcn)
function ()
- attr(*, "srcref")=Class 'srcref' atomic [1:8] 1 18 1 30 18 30 1 1
.. ..- attr(*, "srcfile")=Classes 'srcfilecopy', 'srcfile' <environment:
0x000
000000c00d128>
- attr(*, "foo")= chr "foo"
- attr(*, "class")= chr "foo"
formals(fcn) <- list(a=1)
str(fcn)
function (a = 1)
attributes(fcn)
NULL
TROUBLESHOOTING:
From the definition of formals()<-, it's quite clear why this happens:
`formals<-`
function (fun, envir = environment(fun), value)
{
bd <- body(fun)
as.function(c(value, if (is.null(bd) || is.list(bd)) list(bd) else bd),
envir)
}
<bytecode: 0x000000000b97a848>
<environment: namespace:base>
I'm fine with this, but I just wanted to make sure it's not overlooked.
/Henrik
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