[ANN] hyper search engine 0.2

[Amirouche Boubekki]

Héllo,


Yesterday someone on IRC asked for a new feature; the ability
to use xor/and/not/or to express queries. So here is it!

# Kesako?

The implementation is straight forward. Actually I defined
`xor*`, `and*`, `not*` and `or*` procedures that looks like
this:

```
(define* ((xor* a b) uid)
  (if (procedure? a)
      (if (procedure? b)
          ((xor* (a uid) (b uid)) uid)
          ((xor* (a uid) b) uid))
      (if (procedure? b)
          ((xor* a (b uid)) uid)
          (xor a b))))
```

As you can see it only accepts two arguments :(

Luckily you do no need to understand that to use it,
but it looks funny. That's why I pasted it.

Anyway, given a list of uids that you can retrieve with
`(documents db)` or `(search* db tokens ...)` you can filter
the results with the help of `(keyword db name)`:

```
(filter (and* (keyword db "hypermove") (keyword db "guile")) uids)
```

This is equivalent to `(search* db "hypermove" "guile")` but it is less
efficient!

Previously you could not for instance query the following:

```
(and* (keyword db "commercial") (or* (keyword db "hypermove") (keyword 
db "gnu")))
```

Right now, `keyword` is an implementation detail. But in
the future maybe, you could think of other ways to filter
documents for instance based on some kind of ranking.

# Note on performance

Now a word on `(documents db)`. `documents` does almost
a full scan of a database... To speed things up a little,
you rely on `search*` which is faster but you have
to reword your query. For instance, the previous query,
could actually be done like that:

```
(filter (or* (keyword db "hypermove") (keyword db "gnu")) (search* db 
"commercial"))
```

The documentation is up-to-date on the website:

https://framagit.org/a-guile-mind/hyper


Enjoy!


--
Amirouche ~ amz3 ~ http://www.hyperdev.fr