Re: master 9480169 1/2: Change the string-limit parameter semantics

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Stefan Monnier]

> +@defun string-limit string length &optional end
> +If @var{string} is shorter than @var{length}, @var{string} is returned
> +as is.  Otherwise, return a substring of @var{string} consisting of
> +the first @var{length} characters.  If the optional @var{end}
> +parameter is given, return a string of the @var{length} last
> +characters instead.
>  @end defun

In my experience it's very rare to need to limit a string to
a particular *length*.  Instead you usually want to limit it to
a particular *width*.  So I'd strongly recommend you mention
`truncate-string-to-width` as an alternative.


        Stefan

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Tue, 22 Dec 2020 09:57:26 -0500
> Cc: Lars Ingebrigtsen <larsi@gnus.org>
> 
> In my experience it's very rare to need to limit a string to
> a particular *length*.  Instead you usually want to limit it to
> a particular *width*.

More accurately, almost any code in Emacs that limits strings to some
length, actually ought to limit them to some width instead ;-)

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> In my experience it's very rare to need to limit a string to
>> a particular *length*.  Instead you usually want to limit it to
>> a particular *width*.
>
> More accurately, almost any code in Emacs that limits strings to some
> length, actually ought to limit them to some width instead ;-)

That's true (for limiting lengths for display purposes in Emacs).  This
new function in for when you really want to limit by the number of
characters.  I'll adjust the doc string to point to
`truncate-string-to-width'.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: Stefan Monnier <monnier@iro.umontreal.ca>,  emacs-devel@gnu.org
> Date: Wed, 23 Dec 2020 07:54:32 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > More accurately, almost any code in Emacs that limits strings to some
> > length, actually ought to limit them to some width instead ;-)
> 
> That's true (for limiting lengths for display purposes in Emacs).

Why else would you need to limit a string?

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

> Why else would you need to limit a string?

When talking to APIs with max-length fields; fixed-width data formats;
database columns; etc.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Lars Ingebrigtsen]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> When talking to APIs with max-length fields; fixed-width data formats;
> database columns; etc.

(Of course in some of those you really want a
`string-limit-to-octets-after-encoding-but-shortening-by-characters'
function (which is something I've missed (and implemented a couple of
times)), but it depends.)

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: monnier@iro.umontreal.ca,  emacs-devel@gnu.org
> Date: Wed, 23 Dec 2020 23:25:31 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Why else would you need to limit a string?
> 
> When talking to APIs with max-length fields; fixed-width data formats;
> database columns; etc.

"Columns" as in on display?

Anyway, my point is that almost every string in Emacs eventually gets
displayed.

Re: master 9480169 1/2: Change the string-limit parameter semantics

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> When talking to APIs with max-length fields; fixed-width data formats;
>> database columns; etc.
>
> "Columns" as in on display?

No, as data types -- varchar(100), etc.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no