() Jean Louis <bugs@gnu.support>
() Fri, 13 Nov 2020 15:06:24 +0300

   [tree of knowledge]

Have you tried using a database (like EDB) to hold this info?
(You can find EDB at <https://www.gnuvola.org/software/edb/>.)

   There are options such as filter. And there is option to use
   completing-read to find specific entries or sets of entries.

   The built-in completing-read function does not satisfy my
   needs as it is not as visual and legible. This software works
   well with helm that shows selection in separate split
   window. Other completing packages could work but are more or
   less not as useful as helm.

   My goal is to minimize dependencies and not use neither helm
   nor completing read. I prefer if function is built-in or
   included in Emacs that offers good real-time incremental
   matching or search that narrows selection of lines displayed.

I think the term "narrow" is misguided.  It suggests one locus,
whereas IIUC the behavior you seek is to selectively display
disparate elements in a compact way, w/ unselected elements
completely hidden.  Kind of like an accordian when folded.  So,
adding input would "squeeze" the set of elements, showing those
matching the input and hiding the rest.  Does that sound right?

   - user should be able to type or write anything with spaces
     and words in reverse orders. Matching lines should be
     displayed by first showing:

I don't understand the ordering concept.  What is forward and
what is reverse?  Can you give examples?

     - lines that match all entries, such as "john" "doe"
       "boston" would match entries in that order

     - then eventually would come entries that are not in same
       order, such as those containing first "boston" then
       "john" or "doe" (in any order)

So, it is not really "reverse", but "arbitrary".  Is that right?

Sounds like M-x occur, except dynamic and w/ token permutation.

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