[Swift-devel] "type file;" by default

[Michael Wilde]

I'm in favor of making "file" a built-in type.

I further propose we then use the term "file type" instead of "marker" 
or "mapped" type.

It seems there are at least 2 ways to do so, subtly different:

(a) as if the statement "type file;" has been implicitly executed, or
(b) as if there is a new simple, built-in, mapped type called "file".

(b) seems a bit better, because then the currently unnamed, built-in 
"marker" type gets a name.

If we use alternative (a) above, you would still say:

type Image;
file f;
Image i;

Here, nothing changes except for the built-in definition for "file" - 
not how you *use* the word "file".

With alternative (b), though, you would say:

type Image file;
file f;
Image i;

We could still allow the old style declarations to remain valid (but 
deprecated) for now (or forever), to avoid impact to existing code.

I favor approach (b), because it gives the un-named "marker" type, and 
hence all primitive built-in types, an explicit name. And it looks less 
quirky. But its a minor point.

- Mike



On 2/3/09 5:45 AM, Ben Clifford wrote:
> Pretty much every simple SwiftScript program that I write, I find myself 
> putting in "type file;" at the start, and avoiding "marker types" of the 
> form:
> 
>    type picturefile;
> 
> and thus ignoring application-level type checking (checking that I'm not 
> feeding a picture into a text processing app, and the like) whilst still 
> taking advantage of other swift type checking.
> 
> To simplify low-end uses of the language, it might be useful to have the 
> above "type file;" defined as a built-in type.
> 
> This has been discussed before, but I'd like to know what peoples opinions 
> are.
>