Re: *current-language*

[Andy Wingo <wingo@pobox.com>]

Hello June!

On Sun 12 Jun 2011 03:24, BT Templeton <bpt@hcoop.net> writes:

> What is `*current-language*' supposed to be used for?

It is supposed to be a default language for the compiler and other
things that are interested in languages.

> I see that it's
> set by `(@ (ice-9 eval-string) read-and-eval)' and by `(@ (system base
> compile) read-and-compile)', but not by the REPL.

That's a bug.  Fixed, thanks for the report!

> I think it might be preferable to require explicit language arguments to
> all compilation functions, or to default to Scheme explicitly.

We can change this in 2.2 I think if we want to.  But do we want to?  It
seems like a classic use for dynamic scoping.

> --- a/module/system/base/compile.scm
> +++ b/module/system/base/compile.scm
> @@ -120,9 +120,18 @@
>           (and (false-if-exception (ensure-writable-dir (dirname f)))
>                f))))
>  
> +(define (guess-file-language file)
> +  (cond
> +   ((string-suffix? ".scm" file)
> +    (lookup-language 'scheme))
> +   ((string-suffix? ".el" file)
> +    (lookup-language 'elisp))
> +   (else
> +    (current-language))))
> +
>  (define* (compile-file file #:key
>                         (output-file #f)
> -                       (from (current-language))
> +                       (from (guess-file-language file))

I guess in general I'd prefer something like Racket's #!lang directives,
though I'm not opposed to this approach.  Dunno!

Andy
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