Fwd: declarative syntax

[Asko Kauppi <asko.kauppi@...>]

Really out of my field ;) but..   just a though:

	if not X:fulfills{ in_database, need_data } then
	   get_and_put_in_database (X)
	end

This way, you wouldn't need to duplicate the 'X' for each test 
function. If their prototypes are the same, the 'fulfills' function can 
call them one by one.

-ak


Edelleenlähetetyn viestin alku:

> Lähettäjä: Johann Hibschman <jhibschman@yahoo.com>
> Päiväys: maanantai, 08. maaliskuuta 2004  04:10:43 +0200
> Vastaanottaja: lua list <lua@bazar2.conectiva.com.br>
> Aihe: declarative syntax
> Vastaus: Lua list <lua@bazar2.conectiva.com.br>
>
> Has anyone thought much about doing declarative-style, logic-like 
> programming in Lua?  I know the syntax is supposedly good for such 
> things, but has anyone actually done a backward-chaining engine for 
> Lua?
>
> I want to put together a usable declarative syntax for database and 
> filesystem updates, something where I can merge 'primitive' tests, 
> like:
>
> function last_modified (f) ... end    -- get the last-modified date
> function in_database (rec) ... end    -- check the database
>
> with rules for actions
>
> if not in_database (X) and need_data (X) then
>    get_and_put_in_database (X)
> end
>
> and statements of the state of the world
>
> need_data_for_all {June, July, August, September}
>
> and so on.
>
> I can handle writing your basic horribly-inefficient backward-chaining 
> engine.  I'd have to look up those silly predicate logic terms, but 
> everything is small enough that half-remembered stuff from Intro to AI 
> should be good enough.
>
> What I am having problems with is figuring out how to write those "if" 
> rules in a way that is pretty and readable enough to make the project 
> worthwhile.
>
> Any suggestions?
>
> -Johann