R devel - May 2017 - deparse(substitute(x)) fails in implied call to an S3 print method

In an implied call to an S3 print method, deparse(substitute(x)) returns 
"x", regardless of the name of object in .GlobalEnv, as indicated in
the
following:


 > Xnamed <- 1
 > class(Xnamed) <- 'name.x'
 > print.name.x <- function(x, ...){
+   namex <- deparse(substitute(x))
+   cat('How can I get the name of x in .GlobalEnv?\n',
+       'deparse(substitute(x)) gives only ', namex, '\n')
+ }
 > Xnamed
How can I get the name of x in .GlobalEnv?
  deparse(substitute(x)) gives only  x


       My real application is print.findFn{sos}, which displays in a web 
browser.  If the results of multiple searches are "printed", the name
of
the object in .GlobalEnv could help the user keep track of what was done.

       Thanks,
       Spencer Graves


 > sessionInfo()
R version 3.4.0 (2017-04-21)
Platform: x86_64-apple-darwin15.6.0 (64-bit)
Running under: macOS Sierra 10.12.4

Matrix products: default
BLAS: 
/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
LAPACK: 
/Library/Frameworks/R.framework/Versions/3.4/Resources/lib/libRlapack.dylib

locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods base

loaded via a namespace (and not attached):
[1] compiler_3.4.0 tools_3.4.0

On 07/05/2017 3:56 PM, Spencer Graves wrote:
> In an implied call to an S3 print method, deparse(substitute(x)) returns
> "x", regardless of the name of object in .GlobalEnv, as indicated
in the
> following:
>
>
>  > Xnamed <- 1
>  > class(Xnamed) <- 'name.x'
>  > print.name.x <- function(x, ...){
> +   namex <- deparse(substitute(x))
> +   cat('How can I get the name of x in .GlobalEnv?\n',
> +       'deparse(substitute(x)) gives only ', namex, '\n')
> + }
>  > Xnamed
> How can I get the name of x in .GlobalEnv?
>   deparse(substitute(x)) gives only  x
>
>
>        My real application is print.findFn{sos}, which displays in a web
> browser.  If the results of multiple searches are "printed", the
name of
> the object in .GlobalEnv could help the user keep track of what was done.
I don't think there's any way around this.  Auto-printing of Xnamed 
isn't equivalent to print(Xnamed); it doesn't happen until after Xnamed 
is evaluated.  It assigns the result to a local variable called x, and 
calls print(x).  (All of this is done in C code, and at that point I 
don't think the original expression "Xnamed" is available any
more.)

For your application, you may have to allow users to attach names to the 
object.  I don't know how you're creating those things, but part of the 
work could save a name as an attribute "SOSname", and then the print 
method would use that.

Duncan Murdoch

>
>        Thanks,
>        Spencer Graves
>
>
>  > sessionInfo()
> R version 3.4.0 (2017-04-21)
> Platform: x86_64-apple-darwin15.6.0 (64-bit)
> Running under: macOS Sierra 10.12.4
>
> Matrix products: default
> BLAS:
>
/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
> LAPACK:
> /Library/Frameworks/R.framework/Versions/3.4/Resources/lib/libRlapack.dylib
>
> locale:
> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods base
>
> loaded via a namespace (and not attached):
> [1] compiler_3.4.0 tools_3.4.0
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>

On 2017-05-07 3:46 PM, Duncan Murdoch wrote:
> On 07/05/2017 3:56 PM, Spencer Graves wrote:
>> In an implied call to an S3 print method, deparse(substitute(x))
returns
>> "x", regardless of the name of object in .GlobalEnv, as
indicated in the
>> following:
>>
>>
>>  > Xnamed <- 1
>>  > class(Xnamed) <- 'name.x'
>>  > print.name.x <- function(x, ...){
>> +   namex <- deparse(substitute(x))
>> +   cat('How can I get the name of x in .GlobalEnv?\n',
>> +       'deparse(substitute(x)) gives only ', namex,
'\n')
>> + }
>>  > Xnamed
>> How can I get the name of x in .GlobalEnv?
>>   deparse(substitute(x)) gives only  x
>>
>>
>>        My real application is print.findFn{sos}, which displays in a
web
>> browser.  If the results of multiple searches are "printed",
the name of
>> the object in .GlobalEnv could help the user keep track of what was 
>> done.
>
> I don't think there's any way around this.  Auto-printing of Xnamed
> isn't equivalent to print(Xnamed); it doesn't happen until after 
> Xnamed is evaluated.  It assigns the result to a local variable called 
> x, and calls print(x).  (All of this is done in C code, and at that 
> point I don't think the original expression "Xnamed" is
available any
> more.)
>
> For your application, you may have to allow users to attach names to 
> the object.  I don't know how you're creating those things, but
part
> of the work could save a name as an attribute "SOSname", and then
the
> print method would use that.

       Thanks for the reply.  I'm already saving match.call() and 
displaying that.  That's adequate, but I was hoping to do better.


        Spencer Graves
>
> Duncan Murdoch
>
>
>>
>>        Thanks,
>>        Spencer Graves
>>
>>
>>  > sessionInfo()
>> R version 3.4.0 (2017-04-21)
>> Platform: x86_64-apple-darwin15.6.0 (64-bit)
>> Running under: macOS Sierra 10.12.4
>>
>> Matrix products: default
>> BLAS:
>>
/System/Library/Frameworks/Accelerate.framework/Versions/A/Frameworks/vecLib.framework/Versions/A/libBLAS.dylib
>>
>> LAPACK:
>>
/Library/Frameworks/R.framework/Versions/3.4/Resources/lib/libRlapack.dylib
>>
>>
>> locale:
>> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  methods base
>>
>> loaded via a namespace (and not attached):
>> [1] compiler_3.4.0 tools_3.4.0
>>
>> ______________________________________________
>> R-devel at r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>