As part of a larger program I have created the following functions to convert a list of bits into the integer represents, also to simplify things the order of the bits is reversed [1,1,0,1] represents 1011 (or 13). At the moment the frombin function below works fine.

 

type Bit = Int

 

frombin :: [Bit] -> Int

frombin xs = sum (tonum xs)

 

tonum :: [Bit] -> [Bit]

tonum [] = []

tonum (n:ns) = (n:(tonum (map (*2) ns)))

 

However why when I try the function below does it not work in Hugs?

 

frombin :: [Bit] -> Int

frombin [] = 0

frombin (n:ns) = sum (n:( frombin (map (*2) ns)))

 

Is this surely not just a combination of the two?

 

Any help would be much appreciated

 

Thanks,

Rob