On Thu, Aug 9, 2018 at 4:26 PM jan Vitek <vit...@icloud.com> wrote:
>
> > I'm now confident that I
> > can avoid using "type" by itself, and instead always use it in a
> > compound phrase (like type system) to avoid confusion. That leaves the
> > `.type` argument to many vctrs functions. I'm considering change it to
> > .prototype, because what you actually give it is a zero-length vector
> > of the class you want, i.e. a prototype of the desired output. What do
> > you think of prototype as a name?
>
>
> The term “type system” in computer science is used in very different ways.
> What the note describes is not a type system, but rather a set of
> coercions used by a small number of functions in one package.
>
> Typically it refers to a set of rules (either statically enforced
> by the compiler or dynamically enforced by the runtime) that ensure
> that some particular category of errors can be caught by the
> language.
>
> There is none of that here.
I think there's a bit of that flavour here:
vec_c(factor("a"), Sys.Date())
#> Error: No common type for factor and date
This isn't a type system imposed by the language, but I don't think
that's a reason not to call it a type system.
That said, I agree that calling it a type system is currently
overselling it, and I have made your proposed change to the README
(and added a very-long term goal of making a type system that could be
applied using (e.g.) annotations).
> "The short-term goal of vctrs is to develop a type system for vectors which
> will help reason about functions that combine different types of input (e.g.
> c(), ifelse(), rbind()). The vctrs type system encompasses base vectors (e.g.
> logical, numeric, character, list), S3 vectors (e.g. factor, ordered, Date,
> POSIXct), and data frames; and can be extended to deal with S3 vectors
> defined in other packages, as described in vignette("extending-vctrs”).”
>
> ==>
>
> The short-term goal of vctrs is to specify the behavior of functions that
> combine different types of vectors (e.g. c(), ifelse(), rbind()). The
> specification encompasses base vectors (e.g. logical, numeric, character,
> list), S3 vectors (e.g. factor, ordered, Date, POSIXct), and data frames; and
> can be extended to deal with S3 vectors defined in other packages, as
> described in vignette("extending-vctrs”).
Thanks for the nice wording!
Hadley
--
http://hadley.nz
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