Re: Replace trivial pcase occurrences in the Emacs sources

[Michael Heerdegen]

Eli Zaretskii <address@hidden> writes:

> FWIW, my main problem is not even with cl-case, it's with 'cond'.  It
> seems like we have some 'pcase' epidemic, whose first symptom is that
> people stop using 'cond' and start using 'pcase' instead.  A few
> examples:
>
> todo-mode.el:
>
>     (pcase this-param
>       ('edit (todo-edit-item--text))
>       ('header (todo-edit-item--text 'include-header))
>       ('multiline (todo-edit-item--text 'multiline))
>       ('add/edit (todo-edit-item--text 'comment-edit))
>       ('delete (todo-edit-item--text 'comment-delete))
>       ('diary (todo-edit-item--diary-inclusion))
>       ('nonmarking (todo-edit-item--diary-inclusion 'nonmarking))
>       [...]
>
> auth-source-pass.el:
>
>     (pcase (length matching-entries)
>       (0 (auth-source-pass--do-debug "no match found")
>          nil)
>       (1 (auth-source-pass--do-debug "found 1 match: %s" (car 
> matching-entries))
>          (car matching-entries))
>       (_ (auth-source-pass--select-one-entry matching-entries user)))))
>
> bs.el:
>
>            (setq bs-buffer-show-mark (pcase bs-buffer-show-mark
>                                        (`nil   'never)
>                                        (`never 'always)
>                                        (_       nil))))))
>
> calculator.el:
>
>                (<= inp (pcase calculator-input-radix
>                          (`nil ?9) (`bin ?1) (`oct ?7) (_ 999))))
>
> lpr.el:
>
>                  (pcase (count-lines (point-min) (point-max))
>                    (0 "")
>                    (1 ": ")
>                    (_ ":\n"))

FWIW, these are the major cases I wanted to treat, but I wanted to
replace them with equivalent cl-case forms, not with `cond's.

> (Quick: what's the difference between `require and 'require in this
> case?)

There is none any more.

> easy-mmode.el:
>
>       (pcase keyw
>       (`:group (setq group (nconc group (list :group (pop keys)))))
>       (`:global (setq keys (cdr keys)))
>       (_ (push keyw extra-keywords) (push (pop keys) extra-keywords))))
>
> (Aren't keywords supposed to be self-quoting? then why they are
> explicitly quoted?)

Yes.

> We have dozens of such fragments in our codebase, which just makes the
> sources harder to read, especially for people who aren't fluent with
> 'pcase' (which seems to be the case with many of us).

These are all cases I would want to fix, but unless the whole pcase form
can be trivially rewritten as cl-case, I want to leave pcase, really.


Michael.