Hello,
This is the *third* time I send this, the first two I had a failure
notice so if you have already received it please apologize.
I believe this is consistent with the doc.
From section Value:
formals returns the formal argument list of the function specified, as a
pairlist, or NULL for a non-function or primitive.
So since `+` is primitive formals is expected to return NULL.
Now, as for formals(args(`+`)) once again break it down to its two parts.
> args(`+`)
function (e1, e2)
NULL
Now pass the return value to formals.
> formals(function (e1, e2) NULL)
$e1
$e2
(I first tried this last call with the argument between back ticks and
it didn't work, I wonder why.)
Hope this helps,
Rui Barradas
Às 18:52 de 06/10/2018, Laurent Gautier escreveu:
Hi,
Thanks for the note. How would explain the following snippet taken from
`formals` doc page (the code comment is also from that doc) ?
## formals returns NULL for primitive functions. Use it in combination with
## args for this case.
is.primitive(`+`)
formals(`+`)
formals(args(`+`))
Le sam. 6 oct. 2018 à 13:42, Rui Barradas <ruipbarra...@sapo.pt
<mailto:ruipbarra...@sapo.pt>> a écrit :
Hello,
I believe that this is maybe not a *feature* but at least expected
behaviour.
The call formals(args(`[`)) breaks down to
> args(`[`)
NULL
> formals(NULL)
NULL
Warning message:
In formals(fun) : argument is not a function
Hope this helps,
Rui Barradas
Às 18:26 de 06/10/2018, Laurent Gautier escreveu:
> Hi,
>
> A short code example showing the warning might the only thing
needed here:
>
> ```
>> formals(args(`[`))
> NULL
>
> *Warning message:In formals(fun) : argument is not a function*
>> is.function(`[`)
> [1] TRUE
>> is.primitive(`[`)
> [1] TRUE
> ```
>
> Now with an other primitive:
>
> ```
>> formals(args(`sum`))
> $...
>
>
> $na.rm
> [1] FALSE
>
>> is.function(`sum`)
> [1] TRUE
>> is.primitive(`sum`)
> [1] TRUE
>> class(`[`)
> [1] "function"
> ```
>
> Is this a feature ?
>
>
> Laurent
>
> [[alternative HTML version deleted]]
>
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