And I have sent the email before it was finished, oops. Evaluating at integer values works fine, but trying to do *Main> let a = [-1,2,-6,2] *Main> horner a 1.23 gives this error <interactive>:4:10: No instance for (Fractional Integer) arising from the literal `1.23' Possible fix: add an instance declaration for (Fractional Integer) In the second argument of `horner', namely `1.23' In the expression: horner a 1.23 In an equation for `it': it = horner a 1.23 I know it has something to do with types, but whenever I try to add a type signature to the functions it just messes everything up even more. Any help would be appreciated Thanks, Andrew On Fri, Dec 13, 2013 at 4:03 PM, Andrew Fleckenstein < andrew.fleckenstein@gmail.com> wrote:
Hi all,
I have implemented Horner's method for evaluating a polynomial as follows:
-- the nth horner element, given a list of coefficients and a value at which it needs to be evaluated
horner_element l x n | n == (length l)-1 = last l | otherwise = (l !! n) + (horner_element l x (n+1))*x
-- compute a polynomial given as a list of coefficients at the value x using horner's method.
horner l x = horner_element l x 0