what means "intervals".

what means "intervals".

[Takesi Ayanokoji]

Hi,

I have a question (perhaps a basic English question) about the term
"intervals" used in elisp manual.

This term is used in chapter: Text > section: Text Properties > subsection:
Why Text Properties are not Intervals.
https://www.gnu.org/software/emacs/manual/html_node/elisp/Not-Intervals.html#index-intervals

I Googled this, but I couldn't other meaning but "some amount between two
points".

So I guessed this is "inter-" + "values" means  "internal values".

Am I correct?

Thanks.

Re: what means "intervals".

[Okam]

On 3/8/21 10:30 PM, Takesi Ayanokoji wrote:
>
> Hi,
>
> I have a question (perhaps a basic English question) about the term
> "intervals" used in elisp manual.
>
> This term is used in chapter: Text > section: Text Properties > subsection:
> Why Text Properties are not Intervals.
> https://www.gnu.org/software/emacs/manual/html_node/elisp/Not-Intervals.html#index-intervals
>
> I Googled this, but I couldn't other meaning but "some amount between two
> points".
>
> So I guessed this is "inter-" + "values" means  "internal values".
>
> Am I correct?
>
> Thanks.
>

Hello,

The definition that you found in the correct one. The "interval" is
defined by a beginning position and an ending position in the buffer.
The text found between these two positions is an interval of text.

I read this section as saying that some editors support adding
attributes to text by first defining a range of positions and then
specifying what properties that range of positions should have. Emacs,
on the other hand, works differently, and does not use the concept of a
distinct "interval" object to describe the attributes of text in the buffer.

Re: what means "intervals".

[Stefan Monnier]

> I read this section as saying that some editors support adding
> attributes to text by first defining a range of positions and then
> specifying what properties that range of positions should have. Emacs,
> on the other hand, works differently, and does not use the concept of a
> distinct "interval" object to describe the attributes of text in the buffer.

My take on it is that back during Emacs-19 development, there were
discussions about what kind of functionality to add, where Lucid ended
up going with "extents" whereas the official Emacs tree ended up going
with text-properties (Lucid's "extents" are similar to Emacs's
"overlays"), and this chapter was basically written as a justification
of the choice of text properties over the choice of extents.

This was back during the "great Emacs schism".


        Stefan

Re: what means "intervals".

[Takesi Ayanokoji]

Hello Okam.

Thank you for your clear answer.

I was completely confused, because I read only first  sentence of the
manual description for new function "object-intervals".

http://git.savannah.gnu.org/cgit/emacs.git/tree/doc/lispref/text.texi#n2958

Your answer and checking subsequent example and description, I realized my
mistake.

---
Hello  Stefan.

I am grad to know the reason the term "intervals" was choiced.

I tranlated this term to Japanese term "インターバル" (Katakata English version
of "interval") for elisp-27.1 manual.

In Japanese, Katakata English version "インターバル" has very popular meaning
that mean time amount between two time points.

Because I didn't understand the meaning of "interval" in Emacs clearly,  I
planed changing Japanese term for "interval" if this term has different
meaning.

But now I realize my misunderstanding.

Thanks, and sorry for noise.


2021年3月9日(火) 午後1:21 Stefan Monnier <monnier@iro.umontreal.ca>:

> > I read this section as saying that some editors support adding
> > attributes to text by first defining a range of positions and then
> > specifying what properties that range of positions should have. Emacs,
> > on the other hand, works differently, and does not use the concept of a
> > distinct "interval" object to describe the attributes of text in the
> buffer.
>
> My take on it is that back during Emacs-19 development, there were
> discussions about what kind of functionality to add, where Lucid ended
> up going with "extents" whereas the official Emacs tree ended up going
> with text-properties (Lucid's "extents" are similar to Emacs's
> "overlays"), and this chapter was basically written as a justification
> of the choice of text properties over the choice of extents.
>
> This was back during the "great Emacs schism".
>
>
>         Stefan
>
>
>