facts-db/cl-facts/README.md

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• Hash : ef47623a
  Author : Thomas de Grivel
  Date : 2023-06-19T17:52:01
  

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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)
               (:not movie :is-a :fake))
    (return ?title)))

(defun movie-title (movie)
  (facts:with ((movie :is-a :movie)
               (movie :title ?title)
               (:not movie :is-a :fake))
    (return ?title)))

(defun movie-title (movie)
  (facts:with ((movie :is-a :movie))
    (facts:with ((movie :title ?title))
      (facts:without ((movie :is-a :fake))
        (return ?title)))))

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

Source

• 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://git.kmx.io/facts-db/cl-compare
  * https://git.kmx.io/facts-db/cl-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)
                 (:not movie :is-a :fake))
      (return ?title)))
  ```
  
  is equivalent to
  
  ```common-lisp
  (defun movie-title (movie)
    (facts:with ((movie :is-a :movie)
                 (movie :title ?title)
                 (:not movie :is-a :fake))
      (return ?title)))
  ```
  
  which is itself equivalent to
  
  ```common-lisp
  (defun movie-title (movie)
    (facts:with ((movie :is-a :movie))
      (facts:with ((movie :title ?title))
        (facts:without ((movie :is-a :fake))
          (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.
  

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