New for functional programming

Question

Hey, I'm really new to Haskell and have used more classic programming languages ​​all my life. I have no idea what is going on here. I am trying to make a very simple Viterbi algorithm, but only for two states (fair and dishonest casino)

I have a problem when I want to access an array, but I don’t think I get the types correctly. This or I make a new array every time I try to solve it - equally stupid. Take a look at myArray, te infix, and dynamicProgram, especially PLEASE. Pretty sweet, please.

 Code


import Array
import Char

trans :: Int -> Int -> Double -> Double -> Double
trans from x trans11 trans21 =
    if (from == 1) && (x == 1)
        then trans11
    else if (from == 1) && (x == 2) 
        then (1-trans11)
    else if (from == 2) && (x == 1) 
        then trans21
    else (1-trans21)

em :: Char -> [Double] -> Double
em c list = list!! a
    where a = digitToInt c

intToChar :: Int -> Char
intToChar n | n == 1 = '1'
            | n == 2 = '2'

casino :: Char -> Int -> Int -> [Double] -> [Double] -> Double -> Double -> Double
casino seqchar 1 y em1 em2 t1 t2= 0.5 * (em seqchar em1)
casino seqchar 2 y em1 em2 t1 t2= 0.5 * (em seqchar em2)
casino seqchar x y em1 em2 t1 t2= maximum[ (1 @@ y-1)*(em seqchar em1)*(trans 1 x t1 t2),(2 @@ y-1)*(em seqchar em2)*(trans 2 x t1 t2) ]

dynamicProgram :: [Char] -> (Char -> Int -> Int -> [Double] -> [Double] -> Double -> Double -> Double) -> [Double] -> [Double] -> Double -> Double -> (Array a b)
dynamicProgram string score list1 list2 trans11 trans21 = myArray 1 len
                                [score (string!!y) x y list1 list2 trans11 trans21 | x  Int -> [Double] -> Array a b
myArray startIndex endIndex values = listArray (startIndex,startIndex) (endIndex,endIndex) values

traceback :: [Char] -> Int -> Int -> [Double] -> [Double] -> Double -> Double -> [Char]
traceback s 1 0 em1 em2 t1 t2 = []
traceback s 2 0 em1 em2 t1 t2 = []
traceback s x y em1 em2 t1 t2 | x@@y == (1 @@ y-1)*(em (s!!y) em1)*(trans 1 x t1 t2) = '1' : traceback s 1 (y-1) em1 em2 t1 t2
                            | x@@y == (2 @@ y-1)*(em (s!!y) em1)*(trans 2 x t1 t2) = '2' : traceback s 2 (y-1) em1 em2 t1 t2 

answer :: [Char] -> [Double] -> [Double] -> Double -> Double -> [Char]
answer string list1 list2 t1 t2 = reverse $ maxC : traceback string max end list1 list2 t1 t2 $ dynamicProgram casino string list1 list2 t1 t2
   where
      end = (length string) + 1
      max | maximum (1@@end) (2@@end) == 1@@end = 1
      | maximum (1@@end) (2@@end) == 2@@end = 2
      maxC = intToChar max

infix 5 @@
(@@) i j = myArray ! (i, j)

main = do
    putStrLn "What is the sequence to test?"
    seq  state 1 transmission probability?"
    trp1  state 2 transmission probability is " ++ (1-trp1)
    putStrLn "What is the state 2 -> state 1 transmission probability?"
    trp2  state 2 transmission probability is " ++ (1-trp2)
    putStrLn "I assume that the prob of starting in either state is 1/2.  Go!"
    answer seq st1 st2 trp1 trp2

Answer 1

(- stackoverflow ) ghci, . :

foo.hs:34:71:
    Couldn't match expected type `[e]' against inferred type `(a, b)'
    In the second argument of `listArray', namely
        `(endIndex, endIndex)'
    In the expression:
        listArray (startIndex, startIndex) (endIndex, endIndex) values
    In the definition of `myArray':
        myArray startIndex endIndex values
                  = listArray (startIndex, startIndex) (endIndex, endIndex) values

listArray:

listArray :: (Ix i) => (i, i) -> [e] -> Array i e
        -- Defined in GHC.Arr

. , , , :

listArray (startIndex, endIndex) values

myArray Array a b, Array Int Double.

:

foo.hs:43:44:
    Couldn't match expected type `a -> b'
           against inferred type `[Char]'
    In the first argument of `($)', namely
        `maxC : (traceback string max end list1 list2 t1 t2)'
    In the second argument of `($)', namely
        `(maxC : (traceback string max end list1 list2 t1 t2))
       $ (dynamicProgram casino string list1 list2 t1 t2)'
    In the expression:
          reverse
        $ ((maxC : (traceback string max end list1 list2 t1 t2))
         $ (dynamicProgram casino string list1 list2 t1 t2))

$ , $. , . , , .

:

foo.hs:51:11:
    Couldn't match expected type `Array i e'
           against inferred type `Int -> Int -> [Double] -> Array a b'
    In the first argument of `(!)', namely `myArray'
    In the expression: myArray ! (i, j)
    In the definition of `@@': @@ i j = myArray ! (i, j)

myArray ; , .

, , . myArray, . Haskell, , , , , "" ( , , , ). , .

- , , , @@. , .

:

foo.hs:63:4:
    Couldn't match expected type `[a]' against inferred type `IO ()'
    In the first argument of `(++)', namely
        `putStrLn
           "I assume that the state 1 -> state 2 transmission probability is "'
    In the expression:
          (putStrLn
             "I assume that the state 1 -> state 2 transmission probability is ")
        ++
          (1 - trp1)
    In a 'do' expression:
          (putStrLn
             "I assume that the state 1 -> state 2 transmission probability is ")
        ++
          (1 - trp1)

: , , - , , ​​ , $. , , , ; .

, , . , , :

listArray ((startIndex, startIndex), (endIndex, endIndex)) values

, Array (Int, Int) Double.

Answer 2

:

trans :: Int -> Int -> Double -> Double -> Double
trans 1 1 trans11 trans21 =   trans11
trans 1 2 trans11 trans21 = 1-trans11
trans 2 1 trans11 trans21 =   trans21
trans _ _ trans11 trans21 = 1-trans21