uKanren_translator

Translator miniKanren to Haskell

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A Quick Start

• Install Haskell build tool Stack
• Execute

cd uKanren_translator
stack build
stack exec -- ktrans

The program will pull miniKanren programs from the 'resources' directory, translate them in some directions and put the resulted Haskell programs in the 'test' directory.

Concept by example

You have a miniKanren program appendo. It's a relation, which links 3 lists where the first 2 are concatenation of the third one.

:: appendo x y xy =
  (x === [] /\ xy === y) \/
  ([h t ty:
     x === h % t /\ xy === h % ty /\ {appendo t y ty}])

"It's a relation" means you can execute it in different directions, fixing arguments. For example, if you fix the first two arguments x and y and execute appendo x y, you get concatenation of 2 lists. If you fix the last one and execute appendo xy, you get pairs of all lists, concatenation of which ones gets the list xy.

To make translation in not relational language, you need to choose a direction of translation. As a result, translated appendo x y in Haskell looks like such way:

appendoIIO x0 x1 = appendoIIO0 x0 x1 ++ appendoIIO1 x0 x1
appendoIIO0 s0@[] s1 = do
  let s2 = s1
  return $ (s2)
appendoIIO0 _ _ = []
appendoIIO1 s0@(s3 : s4) s1 = do
  (s5) <- appendoIIO s4 s1
  let s2 = (s3 : s5)
  return $ (s2)
appendoIIO1 _ _ = []

and appendo xy:

appendoOOI x0 = appendoOOI0 x0 ++ appendoOOI1 x0
appendoOOI0 s2@s1 = do
  let s0 = []
  return $ (s0, s1)
appendoOOI0 _ = []
appendoOOI1 s2@(s3 : s5) = do
  (s4, s1) <- appendoOOI s5
  let s0 = (s3 : s4)
  return $ (s0, s1)
appendoOOI1 _ = []

Parsing grammar

Use the next syntax to create a miniKanren program:

Prog   -> Def* Goal
Term   -> Ident | '<' Ident : Term* '>'
Def    -> :: Ident Ident* = Goal
Goal   -> Disj | Fresh | Invoke
Fresh  -> '[' Ident+ ':' Goal ']'
Invoke -> '{' Ident Term* '}'
Disj   -> Conj ('\/' Conj)*
Conj   -> Pat ('/\' Pat)*
Pat    -> Term '===' Term | Fin
Fin    -> Fresh | '(' Disj ')'

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[Internal] Check boxes

• Refactor the translator based on bta
• Add user interface
• Move test execution in Spec
• Update latex files