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GroteTrap

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m (fixed error)
m (improved example)
Line 30: Line 30:
<haskell>
<haskell>
-
> readExpression logicLanguage "p && q"
+
> readExpression logicLanguage "p && q -> r"
-
And [Var "p",Var "q"]
+
Impl (And [Var "p",Var "q"]) (Var "r")
</haskell>
</haskell>
[[Category:Libraries]]
[[Category:Libraries]]

Revision as of 12:38, 24 June 2008

GroteTrap allows you to quickly define expression languages. It is available for download on Hackage.

An example: 

data Logic
  = Var String
  | Or [Logic]
  | And [Logic]
  | Impl Logic Logic
  | Not Logic
  deriving (Show, Eq)
 
logicLanguage :: Language Logic
logicLanguage = language
  { variable  = Var
  , operators =
      [ Unary    Not  Prefix 0 "!"
      , Nary     And  True   1 "&&"
      , Nary     Or   True   2 "||"
      , Binary   Impl InfixR 3 "->"
      ]
  }

With this, we can do: 

> readExpression logicLanguage "p && q -> r"
Impl (And [Var "p",Var "q"]) (Var "r")
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Category: Libraries