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Haskell Quiz/Bytecode Compiler

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(Corrected incorrect tests to match ruby output (3*11%3 == 0, -(2-3-5) == 6))
(Corrected fromBytes to handle negative numbers. Added tests for negative numbers.)
Line 5: Line 5:
 
Use this tester by Michael Sloan:
 
Use this tester by Michael Sloan:
   
<haskell>fromBytes n = foldl (\c (i, n) -> c + n * 2^(i*8) ) 0 . zip [(n-1),(n-2)..0]
+
<haskell>
  +
fromBytes n xs =
  +
let int16 = (fromIntegral ((fromIntegral int32) :: Int16)) :: Int
  +
int32 = byte xs
  +
byte xs = foldl (\accum byte -> (accum `shiftL` 8) .|. (byte)) (head xs) (take (n - 1) (tail xs))
  +
in
  +
if n == 2
  +
then int16
  +
else int32
   
 
interpret [] [] = error "no result produced"
 
interpret [] [] = error "no result produced"
Line 18: Line 18:
 
assert "2+2+2" 6 >> assert "2^8/4" 64 >> assert "3*11%3" 0 >>
 
assert "2+2+2" 6 >> assert "2^8/4" 64 >> assert "3*11%3" 0 >>
 
assert "2*(3+4)" 14 >> assert "(3/3)+(8-2)" 7 >> assert "(1+3)/(2/2)*(10-8)" 8 >> assert "(10%3)*(2+2)" 4 >>
 
assert "2*(3+4)" 14 >> assert "(3/3)+(8-2)" 7 >> assert "(1+3)/(2/2)*(10-8)" 8 >> assert "(10%3)*(2+2)" 4 >>
assert "(10/(2+3)*4)" 8 >> assert "5+((5*4)%(2+1))" 7 >> assert "-(2-3-5)" 6
+
assert "(10/(2+3)*4)" 8 >> assert "5+((5*4)%(2+1))" 7 >> assert "-(2-3-5)" 6 >> assert "-1*-1" (1) >>
  +
assert "1*-1" (-1) >> assert "1*-1" (-1) >> assert "-1*1" (-1) >>
  +
assert "-1" (-1)
 
where assert str val = print ((if (interpret [] $ f str) == val then "Passed: " else "Failed: ") ++ str)</haskell>
 
where assert str val = print ((if (interpret [] $ f str) == val then "Passed: " else "Failed: ") ++ str)</haskell>
   

Revision as of 18:15, 9 November 2006

1 The Problem

Create a bytecode compiler as described on this ruby quiz page: http://www.rubyquiz.com/quiz100.html

Use this tester by Michael Sloan:

fromBytes n xs =
  let int16 = (fromIntegral ((fromIntegral int32) :: Int16)) :: Int
      int32 = byte xs
      byte xs = foldl (\accum byte -> (accum `shiftL` 8) .|. (byte)) (head xs) (take (n - 1) (tail xs))
  in
    if n == 2
    then int16 
    else int32 
 
interpret [] [] = error "no result produced"
interpret (s1:s) [] = s1
interpret s (o:xs) | o < 10 = interpret ((fromBytes (o*2) xs):s) (drop (o*2) xs)
interpret (s1:s2:s) (o:xs)
  | o == 16 = interpret (s2:s1:s) xs
  | otherwise = interpret (((case o of 10 -> (+); 11 -> (-); 12 -> (*); 13 -> (^); 14 -> div; 15 -> mod) s2 s1):s) xs
 
test :: (String -> [Int]) -> IO ()
test f = assert "2+5" 7 >> assert "2-1" 1 >> assert "2*12" 24 >> assert "2^3" 8 >> assert "5/2" 2 >> assert "15%4" 3 >>
         assert "2+2+2" 6 >> assert "2^8/4" 64 >> assert "3*11%3" 0 >>
         assert "2*(3+4)" 14 >> assert "(3/3)+(8-2)" 7 >> assert "(1+3)/(2/2)*(10-8)" 8 >> assert "(10%3)*(2+2)" 4 >>
         assert "(10/(2+3)*4)" 8 >> assert "5+((5*4)%(2+1))" 7 >> assert "-(2-3-5)" 6 >> assert "-1*-1" (1) >>
         assert "1*-1" (-1) >> assert "1*-1" (-1) >> assert "-1*1" (-1) >>
         assert "-1" (-1)
  where assert str val = print ((if (interpret [] $ f str) == val then "Passed: " else "Failed: ") ++ str)

2 Solutions