Warning when calling formals() for `[`.

On 7 Oct 2018, at 16:04 , Rui Barradas <ruipbarradas at sapo.pt> wrote:

Hello,

I don't see why you say that the documentation seems to be wrong:


class(args(`+`))
#[1] "function"


args() on a primitive does return a closure. At least in this case it does.

But in this case it doesn't:

is.primitive(get("["))

[1] TRUE

class(args(get("[")))

[1] "NULL"

Or, for that matter:

is.primitive(`[`)

[1] TRUE

class(args(`[`))

[1] "NULL"

-pd

Rui Barradas

?s 14:05 de 07/10/2018, Peter Dalgaard escreveu:

There is more "fun" afoot here, but I don't recall what the point may be:

args(get("+"))

function (e1, e2)
NULL

args(get("["))

NULL

get("[")

.Primitive("[")

get("+")

function (e1, e2)  .Primitive("+")
The other index operators, "[[", "[<-", "[[<-" are similar
The docs are pretty clear that args() on a primitive should yield a closure, so at least the documentation seems to be wrong.
-pd

On 6 Oct 2018, at 19:26 , Laurent Gautier <lgautier at gmail.com> wrote:

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

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