[r6rs-discuss] Proposed features for small Scheme, part 9: modules

[John Cowan]

Alaric Snell-Pym scripsit:

> Ah-hah. So having feature groups separate like that is a way to allow
> programmers to omit to declare their requirements in order to create
> code that may break unexpectedly? :-)

Pretty much.  Look how things work today:

$ chibi-scheme
> (define x (make-rectangular 1 2))
ERROR: undefined variable: make-rectangular
WARNING: reference to undefined variable: make-rectangular
>

Okay, switch to a different Scheme.  I'm not proposing to change that,
just to add a small amount of introspection so that you can see this
Scheme doesn't support complex numbers.  That's all feature groups are,
really.

Having to import complex numbers from a module, when we know that most
Schemes either have them built in or can't do them at all, is overkill
for a small Scheme.

ObData: I tried the above expression on my usual list of Schemes, and
came up with this:

Returns 1+2i:  PLT, MIT, Gambit, Chicken with numbers egg, scsh/Scheme48,
Kawa, Chez, Ikarus, Larceny, Scheme 7.

Returns 1.0+2.0i: Gauche, SISC, SCM, VScheme.

Error: Chicken, Bigloo, Scheme 9, SScheme, SXM, Chibi.

-- 
John Cowan    cowan at ccil.org    http://ccil.org/~cowan
The present impossibility of giving a scientific explanation is no proof
that there is no scientific explanation. The unexplained is not to be
identified with the unexplainable, and the strange and extraordinary
nature of a fact is not a justification for attributing it to powers
above nature.  --The Catholic Encyclopedia, s.v. "telepathy" (1913)