fix-parser-simple (empty) → 15318.1

raw patch · 4 files changed

+261/−0 lines, 4 filesdep +basesetup-changed

Dependencies added: base

Files

• Parser/Fix/Simple.hs +77/−0
• Setup.hs +2/−0
• fix-parser-simple.cabal +17/−0
• license.txt +165/−0

@@ -0,0 +1,77 @@+{-| Simple fix-expression parser++    If in doubt, just use parsefix+-}++module Parser.Fix.Simple (TokenType (..), Fixity (..), parsefix, foldfix, shunt) where++import Control.Monad;+import Control.Monad.Instances;+import Data.List;+import Data.Maybe;++-- | Fixity/Associativity+data Fixity = Prefix | InfixLeft | InfixRight | InfixNull | Postfix deriving Eq;++data TokenType = -- | Plain, i.e. operand+                 TokenPlain+               | TokenLParenth+               | TokenRParenth+                 -- | Operator, with fixity and precedence+               | TokenOper Fixity Integer+  deriving Eq;++-- | Shunt and Fold+parsefix :: (t -> a, t -> t -> a, t -> t -> t -> a) -> (t -> TokenType) -> [t] -> [a];+parsefix apply = liftM2 (.) (foldfix apply) shunt;++-- | Fold expression in postfix form+foldfix :: (t -> a, t -> t -> a, t -> t -> t -> a) -> (t -> TokenType) -> [t] -> [a];+foldfix (apply0, apply1, apply2) lookup_t =+  let {+    foldfix' _     []     = [];+    foldfix' stack (t:ts) =+      case lookup_t t of {+        TokenPlain -> foldfix' (t:stack) ts;+        TokenOper fix p | fix_arity fix == 2,+                          (x:y:stack') <- stack -> apply2 t x y : foldfix' stack' ts+                        | fix_arity fix == 1,+                          (x:stack')   <- stack -> apply1 t x   : foldfix' stack' ts+                        | otherwise -> error "Malformed fix expression";+        TokenLParenth -> error "Mismatched Parentheses";+        TokenRParenth -> error "Mismatched Parentheses";+       };++    fix_arity Prefix     = 1;+    fix_arity Postfix    = 1;+    fix_arity InfixLeft  = 2;+    fix_arity InfixRight = 2;+    fix_arity InfixNull  = 2;+  } in foldfix' [];++{-| Change from infix to postfix form++    Precedence at start is zero+-}+-- Dijkstra's algorithm+shunt :: (t -> TokenType) -> [t] -> [t];+shunt lookup_t = join . snd . mapAccumR+  (\ stack t ->+   case lookup_t t of {+     TokenPlain -> (stack, [t]);+     TokenOper fix1 p1 | or $ map (== fix1) [InfixLeft, InfixRight, InfixNull] ->+       case map lookup_t stack of {+         (TokenOper fix2 p2 : _) | fix1 == InfixLeft  && p1 <= p2 ||+                                   fix1 == InfixRight && p1 <  p2 ->+               (t : tail stack, [head stack]);+         _ ->  (t : id stack,   []);+       }+                       | Postfix == fix1 -> (  stack, [t])+                       | Prefix  == fix1 -> (t:stack, [])+                       ;+     TokenLParenth -> (t:stack, []);+     TokenRParenth -> case break ((== TokenLParenth) . lookup_t) stack of {+                        (ts, _:stack') -> (stack', ts);+                        (ts, _)        -> (error "Mismatched Parentheses", ts);+                      };+   }) [];

@@ -0,0 +1,2 @@+import Distribution.Simple;+main = defaultMain;

@@ -0,0 +1,17 @@+Name:fix-parser-simple+Version:15318.1+Description:Simple fix-expression parser+License:LGPL+License-File:license.txt+Author:Matthew Farkas-Dyck+Maintainer:strake888@gmail.com+Category:Parser+Synopsis:Simple fix-expression parser+Build-Type:Simple+Cabal-Version: >= 1.2++Library {+  Build-Depends: base >= 4 && < 5+  Extensions: PatternGuards+  Exposed-Modules: Parser.Fix.Simple+}

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