[asdf-devel] Re: :DBG

[Hans Hübner]

Pascal,

if you mean what you write, can you give some reasoning?

-Hans


2013/11/18 Pascal Costanza <pc at p-cos.net>

> DON'T TOUCH THE KEYWORDS PACKAGE! Are you crazy?!?
>
> This will be setting a very bad precedence. Just don't. Really!
>
> Pascal
>
> Sent from my iPad
>
> > On 18 Nov 2013, at 06:17, Faré <fahree at gmail.com> wrote:
> >
> > In ASDF 3.1.0.14, I introduced a macro :DBG (in uiop/utility.lisp).
> > Yes, it's in the keyword package. Why?
> > Because it's the one and only macro I want to be accessible from
> everywhere
> > without a prefix, yet without modifying existing defpackage forms to make
> > it accessible — because it's only used temporarily for debugging.
> >
> > :DBG is a macro for print-debugging. The syntax is
> >   (:DBG tag forms... last-form)
> > The semantics is that if tag is true, print the tag, then for each
> > form, write its source and its values; return the values of the last
> > form. If tag is false, just evaluate the last form and return its
> > values. (Tag is typically a constant keyword or string, identifying
> > the point where values are printed.)
> > The expansion is rather space and time efficient, as far as the
> > semantics permit.
> >
> > I find :DBG soooo useful for print-debugging. I've seen tens of
> > variants of it, but every time with something not quite right in the
> > syntax, semantics or implementation. I just wanted one variant that
> > got everything right, and make it ubiquitous. Because when you need
> > it, you need it now, and there's no time to modify things to load an
> > additional library. And when you're done, you want minimal cleanup,
> > too: just delete the form, except maybe keep the last subform.
> >
> > Previously, I was using (uiop:uiop-debug) from uiop/utility which
> > allows you to load a magic file of your choice that defines a debug
> > mode. The default one I provided was mine, which define :DBG as DBG in
> > your current package (thereby avoiding symbol import issues). But that
> > still adds a new definition everytime and an extra line or form to
> > cleanup.
> >
> > I was recently convinced that using the keyword package instead makes
> > perfect sense: on the one hand, that's using a shared namespace that
> > it is polite to not pollute, but on the other hand, such a temporary
> > print-debugging macro the only use case I imagine of otherwise wanting
> > something to be immediately accessible without package prefixing yet
> > without modifying the package definition form.
> >
> > It's still time to remove that macro before the next release, but I
> > believe it's the right thing to include it, and maybe some of you will
> > agree with me and start using it, if not from the yet unrelease ASDF
> > 3.1.1, perhaps from a copy in your .sbclrc.
> >
> > —♯ƒ • François-René ÐVB Rideau •Reflection&Cybernethics•
> http://fare.tunes.org
> > The common argument that crime is caused by poverty
> > is a kind of slander on the poor.
> >        — H. L. Mencken
> >
>
>
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