On 1 Feb 2008, at 10:30 PM, Logesh Pillay wrote:
I have a list. Each component is a list with 2 whole numbers.
First off, why? In Haskell (unlike dynamically typed languages like Python or Perl), if you know you always have two elements, you want a pair (519432,525806), not a list [519432,525806].
I want to multiply the second number by the log of the first eg tail ([519432,525806]) * log (head [519432,525806]).
You mean [519432,525806] !! 1 * log ([519432,525806 !! 0) or fst (519432,525806) * log (snd (519432,525806) or (best of all) case (519432, 525806) of (x, y) -> x * log y or (if you must have a list) case [519432, 525806] of [x, y] -> x * log y
I get the ffg error message:
No instance for (Floating [t])
This is because tail :: [t] -> [t] It doesn't give you a single element; it gives you the whole list! jcc