[R] serialize does not work as expected

[Duncan Murdoch]

On 29/08/2020 11:34 a.m., Sigbert Klinke wrote:
> Hi,
> 
> if I create a list with
> 
> l <- list(1:3, as.numeric(1:3), c(1,2,3))
> 
> and applying
> 
> lapply(l, 'class')
> lapply(l, 'mode')
> lapply(l, 'storage.mode')
> lapply(l, 'typeof')
> identical(l[[2]], l[[3]])
> 
> then I would believe that as,numeric(1:3) and c(1,2,3) are identical
> objects. However,
> 
> lapply(l, serialize, connection=NULL)
> 
> returns different results for each list element :(
> 
> Any ideas, why it is like that?

Objects like 1:3 are stored in a special compact form, where 1:3 takes 
up the same space as 1:1000000.  Apparently as.numeric() knows to work 
with that special form, and produces the numeric version of it.

You can confirm this by looking at the results of

serialize(l[[i]], connection=stdout(), ascii=TRUE)

for each of i=1,2,3:

 > for (i in 1:3) {
+  cat("\nElement", i, "\n")
+  serialize(l[[i]], connection=stdout(), ascii=TRUE)
+ }

Element 1
A
3
262146
197888
5
UTF-8
238
2
1
262153
14
compact_intseq
2
1
262153
4
base
2
13
1
13
254
14
3
3
1
1
254

Element 2
A
3
262146
197888
5
UTF-8
238
2
1
262153
15
compact_realseq
2
1
262153
4
base
2
13
1
14
254
14
3
3
1
1
254

Element 3
A
3
262146
197888
5
UTF-8
14
3
1
2
3

Notice how element 1 is a "compact_intseq" and element 2 is a 
"compact_realseq".

Duncan Murdoch