Haskell Quiz/Bytecode Compiler
From HaskellWiki
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
- A (non-monadic) solution to the parsing and eval part of this quiz is a case study in Chapter 17 of The Craft of Functional Programming by Simon Thompson.
