[R] POSIXlt class and lapply

[William Dunlap]

Somewhere between R-3.3.3 and R-3.5.2 a POSIXlt method for as.list() was
added, and lapply probably calls as.list().

> RCompare(methods("as.list"))
R version 3.3.3 (2017-03-06)                        | R version 3.5.1
(2018-07-02)
[1] as.list.data.frame      as.list.Date            | [1]
as.list.data.frame      as.list.Date
[3] as.list.default         as.list.environment     | [3] as.list.default
       as.list.environment
[5] as.list.factor          as.list.function        | [5] as.list.factor
      as.list.function
[7] as.list.numeric_version as.list.POSIXct         | [7]
as.list.numeric_version as.list.POSIXct
see '?methods' for accessing help and source code   | [9] as.list.POSIXlt
                                                    | see '?methods' for
accessing help and source code


Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Thu, Feb 14, 2019 at 9:45 AM Newell, Paul <paul.newell using metoffice.gov.uk>
wrote:

> Dear R-helpers,
>
> We have recently upgraded from R-3.3.1 to R-3.5.2.
>
> It seems there has been a change in behaviour of `lapply` and the
> `POSIXlt` class that I cannot find explicitly documented.
>
>
> In R-3.3.1:
>
> > lapply(as.POSIXlt(Sys.Date()), length)
> $sec
> [1] 1
> $min
> [1] 1
> $hour
> [1] 1
> $mday
> [1] 1
> $mon
> [1] 1
> $year
> [1] 1
> $wday
> [1] 1
> $yday
> [1] 1
> $isdst
> [1] 1
>
>
> whereas, in R-3.5.2:
>
> > lapply(as.POSIXlt(Sys.Date()), length)
> [[1]]
> [1] 1
>
>
> Is this change in behaviour intentional?
>
> Realistically, I cannot see anything documented to say that `lapply`
> should behave as per R-3.3.1 on a `POSIXlt` object, so it is/was perhaps
> unwise to rely on it.
>
>
> Best wishes,
> Paul Newell
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