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Re: emacs-25 1d4887a: Improve documentation of 'pcase'

From: Michael Heerdegen
Subject: Re: emacs-25 1d4887a: Improve documentation of 'pcase'
Date: Mon, 25 Jan 2016 17:43:26 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux)

Eli Zaretskii <address@hidden> writes:

> > > > > The possible +alternatives are specified by @var{clauses},
> > > > > each of which must be a +list of the form @code{(@var{pattern}
> > > > > @var{body-forms})}.

> I didn't say body-forms is a list.  I just said that there can be more
> than one form there.

If a (meta) variable has a plural name, it's unexpected in Lisp that
it's not the name of a list or sequence, I think.

> > I just call them pcase patterns.
> Too wordy, IMO.  Try using that in the descriptions of each pattern,
> and you quickly get a mouthful.

In this context it's clear that we speak about pcase, so the generic
term pattern suffices.

> > Strings and floats don't only match themselves, but also any equal
> > string/float.  That's important, since not everything is always tested
> > with `euqal' - multiple occurrences of a symbol are turned into `eq'
> > tests, for example.
> But there's no reference to 'eq' or 'equal' in that text.  It just
> says "matches".

"Themselves" or "itself" in Lisp often means "only this object", that's
why I wanted to be precise.  But I won't argue about that one.

> > > > Maybe we should use
> > > > 
> > > >   @address@hidden(and x (pred numberp) (guard (< x 10)))}}

> There's no reason to believe readers will get such an expression from
> something that is clearly an incomplete fragment.

Ok, let's keep it.

> > > > The thing we name "qpattern" is without backquote, so with the
> > > > current wording, I would leave the backquote out.

> > I think Stefan has answered this question in a different post.
> He just said that he (and evidently you as well) use a different
> "language" when you talk about QPatterns.  I think my "language" is
> more easily understood and matches the actual usage better, even if
> it's pedantically less rigorous.

We speak about a language defined by a formal grammar, you about English
language.  I hope we can make the both fit.  Obscuring the formal
grammar will be confusing to some sort of people, depending on how they
build their mental models.


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