documentation

[fp.git] / src / Lambda.hs

diff --git a/src/Lambda.hs b/src/Lambda.hs
index f54a100..c570199 100644 (file)
--- a/src/Lambda.hs
+++ b/src/Lambda.hs
@@ -1,19 +1,32 @@
 {-# OPTIONS_GHC -fno-warn-unused-do-bind #-}
 {-# LANGUAGE PatternSynonyms #-}
 
 {-# OPTIONS_GHC -fno-warn-unused-do-bind #-}
 {-# LANGUAGE PatternSynonyms #-}
 

-module Lambda where
+-- |
+-- Module      :  Lambda
+-- Copyright   :  Tomáš Musil 2014
+-- License     :  BSD-3
+--
+-- Maintainer  :  tomik.musil@gmail.com
+-- Stability   :  experimental
+--
+-- This is a toy λ-calculus implementation.
+
+module Lambda 
+  ( -- * Types
+    VarName
+  , Term(..)
+    -- * Parsing terms
+  , parseTerm
+  , tRead
+    -- * Reduction
+  , reduce
+  ) where
+  

 
 import Data.Text as T
 import Data.Attoparsec.Text
 import Control.Applicative
 
 
 import Data.Text as T
 import Data.Attoparsec.Text
 import Control.Applicative
 

-type VarName = String
-data Term = Var VarName | Lambda VarName Term | App Term Term deriving (Eq)
-
-pattern RedEx x t s = App (Lambda x t) s
-pattern AppApp a b c = App a (App b c)
-pattern EmLambda x y t = Lambda x (Lambda y t)
-

 -- $setup
 -- >>> import Test.QuickCheck
 -- >>> import Control.Applicative
 -- $setup
 -- >>> import Test.QuickCheck
 -- >>> import Control.Applicative


@@ -21,12 +34,18 @@ pattern EmLambda x y t = Lambda x (Lambda y t)
 -- >>> let aTerm n = oneof [pure (Var "x"), liftA (Lambda "x") $ aTerm (n - 1), liftA2 App (aTerm (n `div` 2)) (aTerm (n `div` 2))] 
 -- >>> instance Arbitrary Term where arbitrary = sized aTerm
 
 -- >>> let aTerm n = oneof [pure (Var "x"), liftA (Lambda "x") $ aTerm (n - 1), liftA2 App (aTerm (n `div` 2)) (aTerm (n `div` 2))] 
 -- >>> instance Arbitrary Term where arbitrary = sized aTerm
 

--- | Read and show λ-terms
---
---   >>> print $ Lambda "x" (Var "x")
---   (λx.x)
---
---   prop> t == tRead (show (t :: Term))
+type VarName = String
+
+-- | 
+-- >>> print $ Lambda "x" (Var "x")
+-- (λx.x)
+
+data Term = Var VarName | Lambda VarName Term | App Term Term deriving (Eq)
+
+-- pattern RedEx x t s = App (Lambda x t) s
+pattern AppApp a b c = App a (App b c)
+pattern EmLambda x y t = Lambda x (Lambda y t)
+

 
 instance Show Term where
   show (Var x) = x
 
 instance Show Term where
   show (Var x) = x


@@ -38,7 +57,9 @@ instance Show Term where
 braced :: Term -> String
 braced t = "(" ++ show t ++ ")"
 
 braced :: Term -> String
 braced t = "(" ++ show t ++ ")"
 

---instance Read Term where
+-- |
+-- prop> t == tRead (show (t :: Term))
+

 tRead :: String -> Term
 tRead s = case parseOnly (parseTerm <* endOfInput) (T.pack s) of
     (Right t) -> t
 tRead :: String -> Term
 tRead s = case parseOnly (parseTerm <* endOfInput) (T.pack s) of
     (Right t) -> t