[Haskell-cafe] recursion problem part 2

[Roelof Wobben]

Jerzy Karczmarczuk schreef op 6-2-2015 om 16:57:
>
> Le 06/02/2015 16:48, Roelof Wobben a écrit :
>> Im only sure that somehow I take the wrong turn somewhere because I 
>> cannot figure out why I do not get the right answer.
>>
>> I think I have the value of n wrong. 
> Did you read my answer entirely? Do so, find the red fat line
>
> You take n=1, and you write:  n<10 not True.
> You don't need to be a specialist on recursion, to see the error.
>
> Jerzy
>

oke,

Another try :

toDigits :: Integer -> [Integer]
toDigits n
    | n < 0 = []
    | n < 10 = [n]
    | otherwise =  toDigits (n `div` 10) ++ [n `mod` 10]

isDigits 1

n < 0 not true.
n < 10 true so [1]

IsDigits 12

n <  0 not true
n < 10 not true
toDigits  1 + [2]

toDigits 1 + [2]

n < 0 not true
n < 10 true [1] ++ [2]

1 ++2 = [1,2]

I think I understand it finnaly.

Roelof