[Rd] WISH: set.seed(seed) to produce error if length(seed) != 1 (now silent)

[GILLIBERT, Andre]

Hello,

A vector with a length >= 2 to set.seed would probably be a bug. An error message will help the user to fix his R code. The bug may be accidental or due to bad understanding of the set.seed function. For instance, a user may think that the whole state of the PRNG can be passed to set.seed.

The "if" instruction, emits a warning when the condition has length >= 2, because it is often a bug. I would expect a warning or error with set.seed().

Validating inputs and emitting errors early is a good practice.

Just my 2 cents.

Sincerely.
Andre GILLIBERT

-----Message d'origine-----
De : R-devel [mailto:r-devel-bounces using r-project.org] De la part de Avraham Adler
Envoyé : vendredi 17 septembre 2021 12:07
À : Henrik Bengtsson
Cc : R-devel
Objet : Re: [Rd] WISH: set.seed(seed) to produce error if length(seed) != 1 (now silent)

Hi, Henrik.

I’m curious, other than proper programming practice, why?

Avi

On Fri, Sep 17, 2021 at 11:48 AM Henrik Bengtsson <
henrik.bengtsson using gmail.com> wrote:

> Hi,
>
> according to help("set.seed"), argument 'seed' to set.seed() should be:
>
>   a single value, interpreted as an integer, or NULL (see ‘Details’).
>
> From code inspection (src/main/RNG.c) and testing, it turns out that
> if you pass a 'seed' with length greater than one, it silently uses
> seed[1], e.g.
>
> > set.seed(1); sum(.Random.seed)
> [1] 4070365163
> > set.seed(1:3); sum(.Random.seed)
> [1] 4070365163
> > set.seed(1:100); sum(.Random.seed)
> [1] 4070365163
>
> I'd like to suggest that set.seed() produces an error if length(seed)
> > 1.  As a reference, for length(seed) == 0, we get:
>
> > set.seed(integer(0))
> Error in set.seed(integer(0)) : supplied seed is not a valid integer
>
> /Henrik
>
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