https://github.com/epost/haskell-ubi-sunt

Predicate logic and relational algebra querying experiments
https://github.com/epost/haskell-ubi-sunt

Last synced: 6 months ago
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Predicate logic and relational algebra querying experiments

• Host: GitHub
• URL: https://github.com/epost/haskell-ubi-sunt
• Owner: epost
• Created: 2015-09-22T20:22:25.000Z (about 10 years ago)
• Default Branch: master
• Last Pushed: 2015-09-22T20:23:02.000Z (about 10 years ago)
• Last Synced: 2025-02-08T07:11:54.812Z (8 months ago)
• Language: Haskell
• Size: 105 KB
• Stars: 1
• Watchers: 2
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.org

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README

          
#+title:Predicate logic and relational algebra querying experiments in Haskell

Evaluating a relational algebra expression (~RelExp~) like this:

#+BEGIN_SRC haskell

main = do

  let

    relExp1 :: RelExp

    relExp1 =

      Project ["fname", "mname", "type"] $

      Select  (AttrEq "type" (AStr "function")) $

      NatJoin (Rel ["f", "type" ] typeAttr) $

      NatJoin (Rel ["m", "mname"] nameAttr) $

      NatJoin (Rel ["f", "m"    ] definedInAttr) $

      RelExp  (Rel ["f", "fname"] nameAttr)

  putStrLn . dumpRel . eval $ relExp1

#+END_SRC

against the following data:

#+BEGIN_EXAMPLE

nameAttr =

  [ [AAtom  1, AStr "map"                    ]

  , [AAtom  2, AStr "ap"                     ]

  , [AAtom  3, AStr "lift2"                  ]

  , [AAtom  4, AStr "lift3"                  ]

  , [AAtom 10, AStr "Control.Functor"        ]

  , [AAtom 11, AStr "Control.Applicative"    ]

  , [AAtom 20, AStr "purescript-functors"    ]

  , [AAtom 21, AStr "purescript-applicative" ]

  ]

definedInAttr =

  [ [AAtom  1, AAtom 10]

  , [AAtom  2, AAtom 11]

  , [AAtom  3, AAtom 11]

  , [AAtom  4, AAtom 11]

  , [AAtom 10, AAtom 20]

  , [AAtom 11, AAtom 21]

  ]

typeAttr =

  [ [AAtom  1, AStr "function" ]

  , [AAtom  2, AStr "function" ]

  , [AAtom  3, AStr "function" ]

  , [AAtom  4, AStr "function" ]

  , [AAtom 10, AStr "module"   ]

  , [AAtom 11, AStr "module"   ]

  , [AAtom 20, AStr "library"  ]

  , [AAtom 21, AStr "library"  ]

  ]

#+END_EXAMPLE

gives us:

#+BEGIN_EXAMPLE

attrs = ["fname","mname","type"]

rows =

  [AStr "map",AStr "Control.Functor",AStr "function"]

  [AStr "ap",AStr "Control.Applicative",AStr "function"]

  [AStr "lift2",AStr "Control.Applicative",AStr "function"]

  [AStr "lift3",AStr "Control.Applicative",AStr "function"]

#+END_EXAMPLE