facts-db/cl-facts/README.md

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• Hash : d0286b85
  Author : Thomas de Grivel
  Date : 2022-11-18T18:33:51
  

  facts-db/cl-facts in-memory graph database
  

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(facts:add ("Blade Runner" :is-a :movie
                           :director "Ridley Scott"
                           :actor "Harison Ford"
                           :actor "Rutger Hauer")
           ("Snow White" :is-a :movie
                         :director "William Cottrell"
                         :director "David Hand"))

(facts:add (?movie :is-a :movie
                   :title "Blade Runner"
                   :director "Ridley Scott"
                   :actor "Harrison Ford"
                   :actor "Rutger Hauer"))

(facts:add (?movie :is-a :movie
                   :title "Snow White and the Seven Dwarfs"
                   :director "William Cottrell"
                   :director "David Hand"))

(facts:rm (?movie :actor "Harison Ford"))

(defun movie-title (movie)
  (facts:with ((movie :is-a :movie
                      :title ?title))
    (return ?title)))

(defun movie-title (movie)
  (facts:with ((movie :is-a :movie)
               (movie :title ?title))
    (return ?title)))

(defun movie-title (movie)
  (facts:with ((movie :is-a :movie))
    (facts:with ((movie :title ?title))
      (return ?title))))

(facts:with ((?movie :is-a :movie
                     :title ?title
                     :director ?director))
  (format t "~A directed ~A~%" ?director ?title))

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• README.md

• facts-db/cl-facts
  =================
  
  > 1.1 The world is the totality of facts, not of things.
  >
  > --  Ludwig Wittgenstein, Tractatus Logico Philosophicus
  
  cl-facts is a small in-memory graph database for Common Lisp.
  It features :
  * a triple store based on unlabelled skip lists
  * a very simple query language (facts:with)
  * transactions using rollback functions
  * logging and replay of transactions to/from disk
  * dumping and loading the database to/from disk
  
  
  Requirements
  ------------
  
  You will need :
  * https://github.com/cl-facts/lessp
  * https://github.com/cl-facts/rollback
  
  
  Usage
  -----
  
  ### FACTS:ADD &rest SPECS
  Adds facts (triples) to the database. Triples can be grouped by subject.
  
  ```common-lisp
  (facts:add ("Blade Runner" :is-a :movie
                             :director "Ridley Scott"
                             :actor "Harison Ford"
                             :actor "Rutger Hauer")
             ("Snow White" :is-a :movie
                           :director "William Cottrell"
                           :director "David Hand"))
  ```
  
  ```common-lisp
  (facts:add (?movie :is-a :movie
                     :title "Blade Runner"
                     :director "Ridley Scott"
                     :actor "Harrison Ford"
                     :actor "Rutger Hauer"))
  
  (facts:add (?movie :is-a :movie
                     :title "Snow White and the Seven Dwarfs"
                     :director "William Cottrell"
                     :director "David Hand"))
  ```
  
  The second version with `?movie` will generate an anonymous symbol prefixed with `movie-`.
  It is considered a more clean and efficient way to abstract identifiers.
  
  ### FACTS:RM &rest SPECS
  ```common-lisp
  (facts:rm (?movie :actor "Harison Ford"))
  ```
  
  ### FACTS:WITH SPECS &body BODY
  
  To follow Wittgenstein's view of the world, all queries get turned into
  testing the presence or absence of triples (facts).
  
  ```common-lisp
  (defun movie-title (movie)
    (facts:with ((movie :is-a :movie
                        :title ?title))
      (return ?title)))
  ```
  
  is equivalent to
  
  ```common-lisp
  (defun movie-title (movie)
    (facts:with ((movie :is-a :movie)
                 (movie :title ?title))
      (return ?title)))
  ```
  
  which is itself equivalent to
  
  ```common-lisp
  (defun movie-title (movie)
    (facts:with ((movie :is-a :movie))
      (facts:with ((movie :title ?title))
        (return ?title))))
  ```
  
  Multiple queries on the same subject can be grouped together easily :
  
  ```common-lisp
  (facts:with ((?movie :is-a :movie
                       :title ?title
                       :director ?director))
    (format t "~A directed ~A~%" ?director ?title))
  ```
  
  ### FACTS:\*DB\*
  The current facts database.
  
  ### FACTS:CLEAR-DB
  Clears the database from every facts.
  
  ### FACTS:SAVE-DB &key INTO (READABLY T)
  Dump the database facts into filespec INTO.
  
  ### FACTS:LOAD-DB SRC
  Load the facts from SRC into \*db\*.
  
  ### FACTS:WITH-TRANSACTION &body BODY
  Enclose BODY database operations into a transaction.
  
  A transaction ensures that all database operations will succeed or be
  reverted using their respective rollback functions.
  
  Transactions can be nested safely.
  
  
  # Licence
  
  cl-facts
  
  Copyright 2011-2022 Thomas de Grivel <thodg@kmx.io>
  
  Permission is hereby granted to use this software granted
  the above copyright notice and this permission paragraph
  are included in all copies and substantial portions of this
  software.
  
  THIS SOFTWARE IS PROVIDED "AS-IS" WITHOUT ANY GUARANTEE OF
  PURPOSE AND PERFORMANCE. IN NO EVENT WHATSOEVER SHALL THE
  AUTHOR BE CONSIDERED LIABLE FOR THE USE AND PERFORMANCE OF
  THIS SOFTWARE.
  

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