Question

A further question about List:

aaa ::  [[(Char, Float)]] -> Float ->  [[(Char, Float)]]
aaa [[]] a = error "no indata"
aaa [[(a,b)]] c = [[(a, b/c)]] 
aaa ([(a,b)]:tail) c = [(a, b/c)] : (aaa tail c)

How to make it work with:

aaa [[('a',3),('b',4),('c',5)],[('a',3),('b',4),('c',5)] ] 4

the result:

[[('a',0.75),('b',1),('c',1.25)],[('a',0.75),('b',1),('c',1.25)]]

Answer 1

how about:

> let l = [[('a',3),('b',4),('c',5)],[('a',3),('b',4),('c',5)] ]
> let aaa list n = map (map (\(c,y) -> (c,(fromIntegral y) / n))) list
> aaa l 4.0
[[('a',0.75),('b',1.0),('c',1.25)],[('a',0.75),('b',1.0),('c',1.25)]]

The types in your snippet down match. You try to apply functions defined on float on integers.
You have to pass floats to the functions. That’s why i convert the integers with (fromIntegral y) to floats before applying the floating point division “/” on them. The second argument has to be a floating point number too, so use 4.0 instead of 4.