to evaluate polynomial in Haskell -

i have function(eval) evaluate polynomial.

eval coeffs value = ....... 

coeffs list of coefficents.

value x in math

ex) calculate 3x^2 + 2x + 1 x=20

coeffs stored reverse order.

when type coefficient above, stored [1,2,3]

program working , last part wrong (the value of polynomial): here code

getcoeff 0 ls =  return ls  getcoeff n ls =  putstr "what x^"             putstr (show(n-1))             putstr " coefficient: "             v <- getline             w <- getcoeff (n-1) ((read v :: float):ls)             return w   evalpoly =   putstr "what degree of polynomial: "         v <- getline             l <- (getcoeff ((read v :: int)+1) [])         putstr "what value want evaluate at: "         x <- getline             putstr "the value of polynomial is: "         putstr (show (polyevaluate (l) (read x :: float)))         putstr "\n"  eval [] x = 0.0 eval (l) x =  

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what degree of polynomial: 2 x^2 coefficient: 3 x^1 coefficient: 2 x^0 coefficient: 1 value want evaluate at: 20 value of polynomial 1241.0 

how can evaluate polynomial coefficient , x value?

some hints...

you can write series of powers easily

powers n = iterate (*n) 1  > take 10 $ powers 2 [1,2,4,8,16,32,64,128,256,512] 

and combine coefficients

> zip [1,2,3] $ powers 20  [(1,1),(2,20),(3,400)] 

you have think change sum of product of pairs (use zipwith)