Re: Should vtable-goto-object use 'equal instead of 'eq?

[Adam Porter <adam@alphapapa.net>]

Hi Kristoffer,

> With these cases in mind, would it be best for vtable-goto-object to
> have as a parameter the predicate used by text-property-search-forward
> (the default being eq)?

Personally, I have no objection to making the predicate a parameter, if 
it's necessary to enable a real use case.

I would suggest that a concrete, real-world use case be presented before 
making such a change; I'm not sure if the example you gave is complete 
enough to be one.

AIUI Vtable is intended to present representations of a collection of 
objects.  Strings are objects, of course, and one can have multiple 
references to a string, which should facilitate comparison with EQ. 
Obviously, if a user inputs a new string that matches one in a 
collection, the two strings would not be EQ, but one could easily use, 
e.g. CL-FIND to locate the matching string and use it for 
VTABLE-GOTO-OBJECT.

As well, I could imagine circumstances in which there could be multiple 
objects in a collection which are EQUAL but not EQ.  Of course, you 
didn't suggest changing the default predicate, so that wouldn't be impacted.

Thinking about it further, making the predicate a parameter would allow 
one to pass a bespoke predicate that could do things like look inside 
objects and compare parts of them, which I could imagine being very 
useful.  (So maybe my suggestion about a concrete use case being 
required is too strong, haha.)

So, if no one else objects, I would be in favor of your suggestion being 
implemented.  It should be just a few lines of code and documentation, 
right?  If you submit a bug/patch, feel free to cc me on it.

--Adam