[R-pkg-devel] Native pipe in package examples

[Serguei Sokol]

Le 26/01/2024 à 10:44, Serguei Sokol a écrit :
> Le 26/01/2024 à 10:31, Serguei Sokol a écrit :
>> Le 25/01/2024 à 19:04, Berwin A Turlach a écrit :
>>> On Thu, 25 Jan 2024 09:44:26 -0800
>>> Henrik Bengtsson <henrik.bengtsson using gmail.com> wrote:
>>>
>>>> On Thu, Jan 25, 2024 at 9:23 AM Berwin A Turlach
>>>> <berwin.turlach using gmail.com> wrote:
>>>>>
>>>>> G'day Duncon,
>>>
>>> Uups, apologies for the misspelling of your name Duncan. Fingers were
>>> too fast. :)
>>>
>>> [...]
>>>>> But you could always code your example (not tested :-) ) along lines
>>>>> similar to:
>>>>>
>>>>> if( with(version, all(as.numeric(c(major, minor)) >= c(4, 1))) ){
>>>>>    ## code that uses native pipe
>>>>> }else{
>>>>>    cat("You have to upgrade to R >= 4.1.0 to run this example\n")
>>>>> }
>>>>
>>>> That will unfortunately not work in this case, because |> is part of
>>>> the new *syntax* that was introduced in R 4.1.0.  Older versions of R
>>>> simply doesn't understand how to *parse* those two symbols next to
>>>> each other, e.g.
>>>>
>>>> {R 4.1.0}> parse(text = "1:3 |> sum()")
>>>> expression(1:3 |> sum())
>>>>
>>>> {R 4.0.5}> parse(text = "1:3 |> sum()")
>>>> Error in parse(text = "1:3 |> sum()") : <text>:1:6: unexpected '>'
>>>> 1: 1:3 |>
>>>>           ^
>>>>
>>>> In order for R to execute some code, it needs to be able to parse it
>>>> first. Only then, it can execute it.  So, here, we're not even getting
>>>> past the parsing phase.
>>>
>>> Well, not withstanding 'fortune(181)', you could code it as:
>>>
>>> if( with(version, all(as.numeric(c(major, minor)) >= c(4, 1))) ){
>>>     cat(eval(parse(text="1:3 |> sum()")), "\n")
>>> }else{
>>>    cat("You have to upgrade to R >= 4.1.0 to run this example\n")
>>> }
>>>
>> By nitpicking a little bit, this test won't work for v5.0 as minor 
>> "0" is less then "1". There are a more canonical ways to test the 
>> version and send a message (or a 'warning()'):
>>
>> if (getVersion() >= "4.1") {
> Oops, it won't work for v10.0. Better would be:
>
> if (utils::compareVersion(getVersion(), "4.1.0") >= 0) {
Sorry for annoyance (not a good day for sending messages), obviously it 
should be 'getRversion()'

Best,
Serguei.

>
> Best,
> Serguei.
>
>> cat(eval(parse(text="1:3 |> sum()")), "\n")
>> } else {
>>    message("You have to upgrade to R >= 4.1.0 to run this example")
>> }
>>
>> Best,
>> Serguei.
>