[racket-dev] Instantiation syntax of `new`

On 02/01/2013 03:29 PM, Asumu Takikawa wrote:
> Hi all,
>
> I've found that when using racket/class, one syntactic pain point I keep
> encountering is that the instantiation is clumsy. This is especially
> true if I want to mix different styles of instantiation (keyword and
> positional).
>
> Is there any reason to not make the instantiation syntax of `new` more
> flexible? I most prefer `new` since it's the shortest and also most
> familiar of the three (the others being `make-object` and
> `instantiate`).
>
> In particular, I'm imagining the following syntax:
>
>    (new c% 1 2 3)       => (instantiate c% (1 2 3))
>    (new c% [x 1] [y 2]) => (instantiate c% [x 1] [y 2])

I think you mean (instantiate c% () [x 1] [y 2]).

>    (new c% [z 3] 1 2)   => (instantiate c% (1 2) [z 3])
>    (new c% 1 [z 3] 2)   => (instantiate c% (1 2) [z 3])
>
> and so on. Attached is a patch that implements this (modulo tests &
> docs). Any thoughts?

It's ambiguous:

   (new c% (x y))

could mean "pass y for initialization argument x" or "pass (x y) as the 
first positional argument".

Ryan