Steel Bank Common Lisp

Henrik Motakef <usenet-reply@...> writes:

> A related question: If I want to express "this function returns only
> one value, a string", do I really have to write '(function (...)
> (values string &optional))'? Apparently, both '(function (...)
> string)' and '(function (...) (values string))' are automagically
> converted to '(function (...) (values &optional string &rest t))'.

This second would appear to be mandated behaviour by the ANSI
specification, in at least one reading.  At least the page for THE
says that missing values in the type specifier default to anything, so
the only way to enforce what you want, portably, would appear to be by
adding the &optional, since FTYPE declarations are equivalent to
wrappping things by equivalent THE forms.

Cheers,

Christophe
-- 
http://www-jcsu.jesus.cam.ac.uk/~csr21/       +44 1223 510 299/+44 7729 383 757
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Henrik Motakef <usenet-reply@...> writes:

> A related question: If I want to express "this function returns only
                                                                 ^^^^^^
                                                                = "exactly"?
> one value, a string", do I really have to write '(function (...)
> (values string &optional))'?

Yes.

> Apparently, both '(function (...)
> string)' and '(function (...) (values string))' are automagically
> converted to '(function (...) (values &optional string &rest t))'.
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I hope you mean (VALUES STRING &REST T): (THE STRING (VALUES)) should
signal a type error.

-- 
Regards,
Alexey Dejneka

"Alas, the spheres of truth are less transparent than those of
illusion." -- L.E.J. Brouwer

Henrik Motakef <usenet-reply@...> writes:

> Hi,
> 
> Is it possible and/or meaningfull to declare the ftype of a generic
> function? It looks like in sbcl (0.8.5), a form like
> 
> (defgeneric foo (x y))
> 
> automatically implies a declaration like
> 
> (ftype (function (t t) *) foo)
> 
> overriding any previous explicit declaration, and issuing a style
> warning about it if they don't match (which they usually don't). Is
> there a way to declare a more strict type for a gf, so that ideally I
> would get neat warning for methods that obviously don't conform to it
> like I would get for ordinary functions?

I think for gfs a combination of types would be the most reasonable type
declaration, e.g. (or (function (string) fixnum) (function (list) fixnum)).
To be practically usable, this should probably adapt dynamically to new
method definitions...

Nicolas.