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Haskell Quiz/Bytecode Compiler/Solution Michael Sloan

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<haskell>import Char(digitToInt)
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[[Category:Haskell Quiz solutions|Bytecode Compiler]]
   
data Tok = C Char | N Int | Op Char | App Tok Tok Tok | G {members :: [Tok]}
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This implementation's only deficiancy is no handling of the negation operator. Proper handling isn't implemented in the ruby quiz tests/solns, however at least basic negative numbers should be included.
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  +
<haskell>import Char(digitToInt)
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import Debug.Trace(trace)
   
  +
data Tok = C Char
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| N Int
  +
| Op Char
  +
| App Tok Tok Tok
  +
| G {members :: [Tok]}
  +
 
--Debugging porpoises
 
--Debugging porpoises
 
instance Show Tok where
 
instance Show Tok where
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show (App a o b) = '(' : (show a) ++ (show o) ++ (show b) ++ ")"
 
show (App a o b) = '(' : (show a) ++ (show o) ++ (show b) ++ ")"
 
show (G xs) = '[' : (concatMap (\x -> show x) xs) ++ "]"
 
show (G xs) = '[' : (concatMap (\x -> show x) xs) ++ "]"
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compile = bytes . parse
 
compile = bytes . parse
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parse xs = stripG $ head $ prec '+' $ prec '-' $ prec '*' $ prec '/' $ prec '^' $ pToks $ parseNOp $ map (\ch -> C ch) xs
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parse = stripG . G . foldr ((.) . prec) id "+-*/%^" . pToks . parseNOp . map C
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parseNOp [] = []
 
parseNOp [] = []
parseNOp ((N num):(C ch):inp) | ch `elem` "0123456789" = parseNOp (N (num * 10 + digitToInt ch) : inp)
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parseNOp ((N num):(C ch):inp)
parseNOp ((C ch):inp) | ch `elem` "0123456789" = parseNOp (N (digitToInt ch) : inp)
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| ch `elem` "0123456789" = parseNOp (N (num * 10 + digitToInt ch) : inp)
parseNOp ((C ch):inp) | ch `elem` "+-*/^%" = parseNOp (Op ch : inp)
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parseNOp ((C ch):inp) | ch `elem` "0123456789" = parseNOp (N (digitToInt ch) : inp)
parseNOp ((C ch):inp) | ch `elem` " \t\r\n" = parseNOp inp
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parseNOp ((C ch):inp) | ch `elem` "+-*/^%" = parseNOp (Op ch : inp)
parseNOp (a:inp) = a : (parseNOp inp)
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parseNOp ((C ch):inp) | ch `elem` " \t\r\n" = parseNOp inp
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parseNOp ((C ch):inp) | ch `elem` "()" = (C ch) : (parseNOp inp)
  +
parseNOp ((C ch):inp) = trace ("Skipped char '"++[ch]) (parseNOp inp)
  +
parseNOp (x:inp) = x : (parseNOp inp)
  +
 
--Groups an array of tokens if it needs to be
 
--Groups an array of tokens if it needs to be
 
g (x:xs) | null xs = x
 
g (x:xs) | null xs = x
 
g xs = G xs
 
g xs = G xs
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--Returns parsed tokens/stream remainder
 
--Returns parsed tokens/stream remainder
 
pToks = fst . parseG
 
pToks = fst . parseG
pRem = snd . parseG
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pRem = snd . parseG
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parseG [] = ([], [])
 
parseG [] = ([], [])
 
parseG [(G ts)] = (ts, [])
 
parseG [(G ts)] = (ts, [])
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parseG ((C ')') : inp) = ([], inp)
 
parseG ((C ')') : inp) = ([], inp)
 
parseG (i:inp) = (i : (pToks inp), pRem inp)
 
parseG (i:inp) = (i : (pToks inp), pRem inp)
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  +
aPrec mo a (Op o) b = App (g $ prec mo [a]) (Op o) (g $ prec mo [b])
  +
 
--Traverses groups, applies operators to their immediate arguments
 
--Traverses groups, applies operators to their immediate arguments
 
prec mo [] = []
 
prec mo [] = []
prec mo ((G xs):inp) = (g $ prec mo xs) : (prec mo inp)
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prec mo (a:(Op o):b:inp) | o == mo = prec mo ((aPrec mo a (Op o) b) : inp)
prec mo (a:(Op o):b:inp) | o == mo = prec mo ((App (g $ prec mo [a]) (Op o) (g $ prec mo [b])) : inp)
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prec mo ((G xs):inp) = (g $ prec mo xs) : (prec mo inp)
prec mo ((App a o b):inp) = (App (g $ prec mo [a]) o (g $ prec mo [b])) : (prec mo inp)
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prec mo ((App a o b):inp) = (aPrec mo a o b) : (prec mo inp)
 
prec mo (x:inp) = x : (prec mo inp)
 
prec mo (x:inp) = x : (prec mo inp)
+
 
--Removes any vestigial grouping
 
--Removes any vestigial grouping
 
stripG (App a o b) = App (stripG a) o (stripG b)
 
stripG (App a o b) = App (stripG a) o (stripG b)
stripG (G (x:xs)) | null xs = error $ "error: " ++ show (x:xs) ++ " <- improper infix nesting here"
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stripG (G (x:xs)) | null xs = stripG x
stripG (G (x:xs)) = stripG x
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stripG (G (x:xs)) = error $ "error: " ++ show (x:xs) ++ " <- improper infix nesting here"
 
stripG x = x
 
stripG x = x
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--Converts to a byte format
 
--Converts to a byte format
 
bytes (C x) = error ("Invalid character: " ++ [x])
 
bytes (C x) = error ("Invalid character: " ++ [x])
bytes (N n) = if abs n < 2^15 then 1 : toByteArray n 2 else 2 : toByteArray n 4
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bytes (N n) = if abs n < 2^15 then 1 : toBytes 2 n else 2 : toBytes 4 n
bytes (Op ch) = case ch of '+' -> [10]; '*' -> [11]; '^' -> [12]; '/' -> [14]; '%' -> [15]
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bytes (Op ch) = case ch of '+' -> [10]; '-' -> [11]; '*' -> [12]; '^' -> [13]; '/' -> [14]; '%' -> [15]
 
bytes (App a o b) = (bytes a) ++ (bytes b) ++ (bytes o)
 
bytes (App a o b) = (bytes a) ++ (bytes b) ++ (bytes o)
 
bytes x = error ("Error, invalid: " ++ show x)
 
bytes x = error ("Error, invalid: " ++ show x)
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toByteArray x n = map (\i -> (x `div` 2^(i*8)) `mod` 256 ) [(n-1),(n-2)..0]</haskell>
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toBytes n x = map (\i -> (x `div` 2^(i*8)) `mod` 256 ) [(n-1),(n-2)..0]</haskell>

Latest revision as of 10:43, 13 January 2007


This implementation's only deficiancy is no handling of the negation operator. Proper handling isn't implemented in the ruby quiz tests/solns, however at least basic negative numbers should be included.

import Char(digitToInt)
import Debug.Trace(trace)
 
data Tok = C   Char
         | N   Int
         | Op  Char
         | App Tok Tok Tok
         | G {members :: [Tok]}
 
--Debugging porpoises
instance Show Tok where
    show (C ch) = ch : ""
    show (N i) = show i
    show (Op ch) = ch : ""
    show (App a o b) = '(' : (show a) ++ (show o) ++ (show b) ++ ")"
    show (G xs) = '[' : (concatMap (\x -> show x) xs) ++ "]"
 
compile = bytes . parse
 
parse = stripG . G . foldr ((.) . prec) id "+-*/%^" . pToks . parseNOp . map C
 
parseNOp [] = []
parseNOp ((N num):(C ch):inp)
                      | ch `elem` "0123456789" = parseNOp (N (num * 10 + digitToInt ch) : inp)
parseNOp ((C ch):inp) | ch `elem` "0123456789" = parseNOp (N (digitToInt ch) : inp)
parseNOp ((C ch):inp) | ch `elem` "+-*/^%"     = parseNOp (Op ch : inp)
parseNOp ((C ch):inp) | ch `elem` " \t\r\n"    = parseNOp inp
parseNOp ((C ch):inp) | ch `elem` "()"         = (C ch) : (parseNOp inp)
parseNOp ((C ch):inp)                          = trace ("Skipped char '"++[ch]) (parseNOp inp)
parseNOp (x:inp)                               = x : (parseNOp inp)
 
--Groups an array of tokens if it needs to be
g (x:xs) | null xs = x
g xs = G xs
 
--Returns parsed tokens/stream remainder
pToks = fst . parseG
pRem  = snd . parseG
 
parseG []              = ([], [])
parseG [(G ts)]        = (ts, [])
parseG ((C '(') : inp) = (g (pToks inp) : (pToks $ pRem inp), []) 
parseG ((C ')') : inp) = ([], inp)
parseG (i:inp)         = (i : (pToks inp), pRem inp)
 
aPrec mo a (Op o) b = App (g $ prec mo [a]) (Op o) (g $ prec mo [b])
 
--Traverses groups, applies operators to their immediate arguments
prec mo [] = []
prec mo (a:(Op o):b:inp) | o == mo = prec mo ((aPrec mo a (Op o) b) : inp)
prec mo ((G xs):inp)               = (g $ prec mo xs) : (prec mo inp)
prec mo ((App a o b):inp)          = (aPrec mo a o b) : (prec mo inp)
prec mo (x:inp) = x : (prec mo inp)
 
--Removes any vestigial grouping
stripG (App a o b) = App (stripG a) o (stripG b)
stripG (G (x:xs)) | null xs = stripG x
stripG (G (x:xs)) = error $ "error: " ++ show (x:xs) ++ " <- improper infix nesting here"
stripG x = x
 
--Converts to a byte format
bytes (C x) = error ("Invalid character: " ++ [x])
bytes (N n) = if abs n < 2^15 then 1 : toBytes 2 n else 2 : toBytes 4 n
bytes (Op ch) = case ch of '+' -> [10]; '-' -> [11]; '*' -> [12]; '^' -> [13]; '/' -> [14]; '%' -> [15]
bytes (App a o b) = (bytes a) ++ (bytes b) ++ (bytes o)
bytes x = error ("Error, invalid: " ++ show x)
 
toBytes n x = map (\i -> (x `div` 2^(i*8)) `mod` 256 ) [(n-1),(n-2)..0]