R devel - Oct 2015 - A where() functions that does what exists() does but return the environment when object lives?

Hi,

exists("foo", inherits=TRUE) check whether an object named
"foo"
exists, and get("foo", inherits=TRUE) retrieves it.  I'm looking
for a
similar function to exists() that returns the environment where the
object "foo" exists, iff at all.  If not found, NULL is returned.
Does that exist?

EXAMPLE #1:
> sample2 <- base::sample
> env <- where("sample2", inherits=TRUE)
> env
<environment: R_GlobalEnv>

Note the difference to:
> obj <- get("sample2", inherits=TRUE)
> environment(obj)
<environment: namespace:base>


EXAMPLE #2:
> a <- 1
> foo <- function() { b <- 2; list(a=where("a",
inherits=TRUE), b=where("b", inherits=TRUE)) }
> foo()
$a
<environment: R_GlobalEnv>
$b
<environment: 0x000000000b7d2798>
> foo()
$a
<environment: R_GlobalEnv>
$b
<environment: 0x000000000b7d23e0>


I do understand that I can implement such a function myself, but I
prefer not to.

Thanks,

Henrik

I'd start looking at getAnywhere().

Best,
Uwe

On 10.10.2015 01:18, Henrik Bengtsson wrote:
> Hi,
>
> exists("foo", inherits=TRUE) check whether an object named
"foo"
> exists, and get("foo", inherits=TRUE) retrieves it.  I'm
looking for a
> similar function to exists() that returns the environment where the
> object "foo" exists, iff at all.  If not found, NULL is returned.
> Does that exist?
>
> EXAMPLE #1:
>
>> sample2 <- base::sample
>> env <- where("sample2", inherits=TRUE)
>> env
> <environment: R_GlobalEnv>
>
> Note the difference to:
>
>> obj <- get("sample2", inherits=TRUE)
>> environment(obj)
> <environment: namespace:base>
>
>
> EXAMPLE #2:
>
>> a <- 1
>> foo <- function() { b <- 2; list(a=where("a",
inherits=TRUE), b=where("b", inherits=TRUE)) }
>> foo()
> $a
> <environment: R_GlobalEnv>
> $b
> <environment: 0x000000000b7d2798>
>
>> foo()
> $a
> <environment: R_GlobalEnv>
> $b
> <environment: 0x000000000b7d23e0>
>
>
> I do understand that I can implement such a function myself, but I
> prefer not to.
>
> Thanks,
>
> Henrik
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

On Sat, Oct 10, 2015 at 1:24 AM, Uwe Ligges
<ligges at statistik.tu-dortmund.de> wrote:
> I'd start looking at getAnywhere().
Thanks Uwe, that does indeed provides "where" information.
Unfortunately, I don't see how it will allow me to search environments
similarly/in the same order as exists/get(..., envir, inherits=TRUE)
does it.  getAnywhere() will search everything in any order.  It's a
start though.

Cheers,

Henrik
>
> Best,
> Uwe
>
>
> On 10.10.2015 01:18, Henrik Bengtsson wrote:
>>
>> Hi,
>>
>> exists("foo", inherits=TRUE) check whether an object named
"foo"
>> exists, and get("foo", inherits=TRUE) retrieves it.  I'm
looking for a
>> similar function to exists() that returns the environment where the
>> object "foo" exists, iff at all.  If not found, NULL is
returned.
>> Does that exist?
>>
>> EXAMPLE #1:
>>
>>> sample2 <- base::sample
>>> env <- where("sample2", inherits=TRUE)
>>> env
>>
>> <environment: R_GlobalEnv>
>>
>> Note the difference to:
>>
>>> obj <- get("sample2", inherits=TRUE)
>>> environment(obj)
>>
>> <environment: namespace:base>
>>
>>
>> EXAMPLE #2:
>>
>>> a <- 1
>>> foo <- function() { b <- 2; list(a=where("a",
inherits=TRUE),
>>> b=where("b", inherits=TRUE)) }
>>> foo()
>>
>> $a
>> <environment: R_GlobalEnv>
>> $b
>> <environment: 0x000000000b7d2798>
>>
>>> foo()
>>
>> $a
>> <environment: R_GlobalEnv>
>> $b
>> <environment: 0x000000000b7d23e0>
>>
>>
>> I do understand that I can implement such a function myself, but I
>> prefer not to.
>>
>> Thanks,
>>
>> Henrik
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

Seems easy enough to write yourself:

where <- function(x, env = parent.frame()) {
    if (identical(env, emptyenv()))
        return(NULL)
    if (exists(x, envir = env, inherits = FALSE))
        return(env)
    where(x, parent.env(env))
}

sample2 <- base::sample
where("sample2")
#> <environment: 0x1154d3c28>
where("sample")
#> <environment: base>
where("blah")
#> NULL

Hadley

On Fri, Oct 9, 2015 at 6:18 PM, Henrik Bengtsson
<henrik.bengtsson at ucsf.edu> wrote:
> Hi,
>
> exists("foo", inherits=TRUE) check whether an object named
"foo"
> exists, and get("foo", inherits=TRUE) retrieves it.  I'm
looking for a
> similar function to exists() that returns the environment where the
> object "foo" exists, iff at all.  If not found, NULL is returned.
> Does that exist?
>
> EXAMPLE #1:
>
>> sample2 <- base::sample
>> env <- where("sample2", inherits=TRUE)
>> env
> <environment: R_GlobalEnv>
>
> Note the difference to:
>
>> obj <- get("sample2", inherits=TRUE)
>> environment(obj)
> <environment: namespace:base>
>
>
> EXAMPLE #2:
>
>> a <- 1
>> foo <- function() { b <- 2; list(a=where("a",
inherits=TRUE), b=where("b", inherits=TRUE)) }
>> foo()
> $a
> <environment: R_GlobalEnv>
> $b
> <environment: 0x000000000b7d2798>
>
>> foo()
> $a
> <environment: R_GlobalEnv>
> $b
> <environment: 0x000000000b7d23e0>
>
>
> I do understand that I can implement such a function myself, but I
> prefer not to.
>
> Thanks,
>
> Henrik
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel


-- 
http://had.co.nz/

On Tue, Oct 13, 2015 at 4:43 PM, Hadley Wickham <h.wickham at gmail.com>
wrote:
> Seems easy enough to write yourself:
>
> where <- function(x, env = parent.frame()) {
>     if (identical(env, emptyenv()))
>         return(NULL)
>     if (exists(x, envir = env, inherits = FALSE))
>         return(env)
>     where(x, parent.env(env))
> }
>
> sample2 <- base::sample
> where("sample2")
> #> <environment: 0x1154d3c28>
And that returns a random environment because I ran it with
reprex::reprex().  In interactive use it will return <environment:
R_GlobalEnv>

Hadley

-- 
http://had.co.nz/