Re: [Rd] Surpising behavior when using an active binding as loop index in R 4.0.0

2020-05-23 Thread Thomas Friedrichsmeier via R-devel 
Possibly just a symptom of the earlier behavior, but I'll amend my
example, below, with an even more disturbing observation:

Am Sat, 23 May 2020 13:19:24 +0200
schrieb Thomas Friedrichsmeier via R-devel :
[...]
> Consider the code below:
> 
> makeActiveBinding("i", 
>   function(value) {
>   if (missing(value)) {
>   x
>   } else {
>   print("set")
>   x <<- value
>   }
>   }, globalenv())
> 
> i <- 1 # output "set"
> print(i)   # output [1] 1
> 
> # Surprising behavior starts here:
> for(i in 2:3) print(i) # output [1] "set"
>#NULL
>#NULL
> 
> print(i)   # output NULL
> print(x)   # output NULL
> 
> i <- 4 # output "set"
> print(i)   # ouput [1] 4
> print(x)   # ouput [1] 4

ls()
# Error in ls() : 
#  Value of SET_STRING_ELT() must be a 'CHARSXP' not a 'NULL'

Regards
Thomas


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[Rd] Surpising behavior when using an active binding as loop index in R 4.0.0

2020-05-23 Thread Thomas Friedrichsmeier via R-devel 
Hi,

I stumbled upon a surprising behavior when using an active binding as a
loop index variable in R 4.0.0. In contrast, the behavior observed in R
3.6.1 is in line with my expectations.

Consider the code below:

makeActiveBinding("i", 
function(value) {
if (missing(value)) {
x
} else {
print("set")
x <<- value
}
}, globalenv())

i <- 1 # output "set"
print(i)   # output [1] 1

# Surprising behavior starts here:
for(i in 2:3) print(i) # output [1] "set"
   #NULL
   #NULL

print(i)   # output NULL
print(x)   # output NULL

i <- 4 # output "set"
print(i)   # ouput [1] 4
print(x)   # ouput [1] 4

Regards
Thomas


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