From dwinsemius at comcast.net  Wed Jul 15 22:25:11 2015
From: dwinsemius at comcast.net (David Winsemius)
Date: Wed, 15 Jul 2015 13:25:11 -0700
Subject: [Rd] bquote/evalq behavior changed in R-3.2.1
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On Jul 15, 2015, at 12:51 PM, William Dunlap wrote:

> I think rapply() was changed to act like lapply() in this respect.
> 

When I looked at the source of the difference, it was that typeof() returned 'language' in 3.2.1, while it returned 'list' in the earlier version of R. The first check in rapply's code in both version was:

 if (typeof(object) != "list") 
        stop("'object' must be a list")

Wrapping list() around the first argument and switching to using eval with an expression-object rather than a call-object seemed to solve the problem when this was posed as a question on StackOverflow, but Dayne was not happy with that solution for other reasons that he is not describing.

-- 
David.

> In R-3.1.3 we got
> rapply(list(quote(1+myNumber)), evalq, envir=list2env(list(myNumber=17)))
> #[1] 18
> rapply(list(quote(1+myNumber)), eval, envir=list2env(list(myNumber=17)))
> #Error in (function (expr, envir = parent.frame(), enclos = if
> (is.list(envir) ||  :
>  object 'myNumber' not found
> lapply(list(quote(1+myNumber)), evalq, envir=list2env(list(myNumber=17)))
> #Error in eval(substitute(expr), envir, enclos) : object 'X' not found
> lapply(list(quote(1+myNumber)), eval, envir=list2env(list(myNumber=17)))
> #[[1]]
> #[1] 18
> while in R-3.2.0 we get
> rapply(list(quote(1+myNumber)), evalq, envir=list2env(list(myNumber=17)))
> #Error in eval(substitute(expr), envir, enclos) : object 'X' not found
> rapply(list(quote(1+myNumber)), eval, envir=list2env(list(myNumber=17)))
> #[1] 18
> lapply(list(quote(1+myNumber)), evalq, envir=list2env(list(myNumber=17)))
> #Error in eval(substitute(expr), envir, enclos) : object 'X' not found
> lapply(list(quote(1+myNumber)), eval, envir=list2env(list(myNumber=17)))
> #[[1]]
> #[1] 18
> 
> Make the FUN argument function(arg)sys.call() to see some details of the
> change.
> 
> 
> Bill Dunlap
> TIBCO Software
> wdunlap tibco.com
> 
> On Wed, Jul 15, 2015 at 12:35 PM, Dayne Filer <dayne.filer at gmail.com> wrote:
> 
>> In 3.1.2 eval does not store the result of the bquote-generated call in
>> the given environment. Interestingly, in 3.2.1 eval does store the result
>> of the bquote-generated call in the given environment.
>> 
>> In other words if I run the given example with eval rather than evalq, on
>> 3.1.2 "x" is never stored in "fenv," but it is when I run the same code on
>> 3.2.1. However, the given example stores "x" in "fenv" on 3.1.2, but throws
>> the error I gave when run on 3.2.1.
>> 
>> To give credit, I received the idea for using evalq from SO:
>> http://stackoverflow.com/a/22559385
>> 
>> Dayne
>> 
>> 
>> On Wed, Jul 15, 2015 at 3:29 PM, William Dunlap <wdunlap at tibco.com> wrote:
>> 
>>> I am curious why you used evalq instead of eval in this code.
>>> 
>>> Bill Dunlap
>>> TIBCO Software
>>> wdunlap tibco.com
>>> 
>>> On Wed, Jul 15, 2015 at 11:49 AM, Dayne Filer <dayne.filer at gmail.com>
>>> wrote:
>>> 
>>>> Hello,
>>>> 
>>>> I upgraded from 3.1.2 to 3.2.1 and am receiving errors on code that
>>>> worked
>>>> as I intended previously. Briefly, I am using bquote to generate
>>>> expressions to modify data.table objects within a  function, so I need
>>>> the
>>>> changes to actually be stored in the given environment. Previously, I
>>>> used
>>>> code like the following:
>>>> 
>>>> test <- list(bquote(x <- 10))
>>>> fenv <- environment()
>>>> rapply(test, evalq, envir = fenv)
>>>> 
>>>> Although the code in the example above is much simpler, it shows the
>>>> problem. On 3.1.2 the expression is evaluated and x is stored as 10 in
>>>> the
>>>> given environment, fenv. In 3.2.1 the code throws an error:
>>>> 
>>>> Error in eval(substitute(expr), envir, enclos) : object 'X' not found
>>>> 
>>>> I could not find anything in the release notes that would explain this
>>>> change. Changing evalq to eval works in 3.2.1, but eval does not store x
>>>> in
>>>> the given environment in 3.1.2.
>>>> 
>>>> Thanks,
>>>> 
>>>> Dayne
>>>> 
>>>>        [[alternative HTML version deleted]]
>>>> 
>>>> ______________________________________________
>>>> R-devel at r-project.org mailing list
>>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>>> 
>>> 
>>> 
>> 
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel

David Winsemius
Alameda, CA, USA



[Rd] bquote/evalq behavior changed in R-3.2.1
David Winsemius