How about text-property-functions using `equal' rather than `eq'?

How about text-property-functions using `equal' rather than `eq'?

[Alan Mackenzie]

Hi, Emacs!

All the built in text property functions which compare properties appear
to use `eq' for the comparison.  Some of these actually say this in
their doc-strings or the pertinent manual page, some of them might
actually say it in both.  ;-(

However, it seems to me that `equal' would be a better comparison.  I am
currently playing with syntax-table text-properties, and some characters
need to have the property set to '(1) (i.e. punctuation).

I would dearly love to use text-property-any to locate such a buffer
position, but unfortunately (eq '(1) '(1)) => nil.  :-(  So I've had to
code up a clumsy equivalent which will certainly be much slower.

Would it not be a good idea to change these functions to use `equal'
instead?  No, it wouldn't be a good idea.

How about providing each of these with an optional extra parameter, the
comparison predicate?  A much better idea!  So we'd have, for example:

  (defun text-property-any (start end prop value &optional object pred)

, with PRED defaulting to `eq'.

-- 
Alan Mackenzie (Nuremberg, Germany)

Re: How about text-property-functions using `equal' rather than `eq'?

[Richard Stallman]

    All the built in text property functions which compare properties appear
    to use `eq' for the comparison.  Some of these actually say this in
    their doc-strings or the pertinent manual page, some of them might
    actually say it in both.  ;-(

`eq' is faster, and a priori I see no reason to think that `equal'
is better in general.

    I would dearly love to use text-property-any to locate such a buffer
    position, but unfortunately (eq '(1) '(1)) => nil.  :-(  So I've had to
    code up a clumsy equivalent which will certainly be much slower.

You can write code which uses the primitives to find the next non-eq
property, then comparing it with equal and looping so that you find
the next non-equal property.

Re: How about text-property-functions using `equal' rather than `eq'?

[David Kastrup]

Richard Stallman <rms@gnu.org> writes:

>     All the built in text property functions which compare properties appear
>     to use `eq' for the comparison.  Some of these actually say this in
>     their doc-strings or the pertinent manual page, some of them might
>     actually say it in both.  ;-(
>
> `eq' is faster,

More importantly, it is constant time.

>     I would dearly love to use text-property-any to locate such a
>     buffer position, but unfortunately (eq '(1) '(1)) => nil.  :-( So
>     I've had to code up a clumsy equivalent which will certainly be
>     much slower.
>
> You can write code which uses the primitives to find the next non-eq
> property, then comparing it with equal and looping so that you find
> the next non-equal property.

One can also see where the constant '(1) is created and keep a copy of
that for eq-comparison.

-- 
David Kastrup