>> Karczmarczuk’s solution via the Haskell prelude:
>>
>> part = 1 : b 1
>>   where b n = (1 : b (n + 1)) + (replicate n 0 ++ b n)
>>

> This is broken code, no?, just 2 reasons I can spot why:
> - function 'b n' calls 'b n' unconditionally (infite loop)
> - What is the reutrn type of 'b'? It seems like it returns list, but the
 >  return value is in the form 'a + b' , where (+) is instance of num so

 >  I don't think prelude contains any ad-hoc definition of (+) that

 >  returns list

Not broken, just insufficiently documented.  "part "is supposed to produce an infinite stream whose nth element is the number of distinct representations of n as a sum of positive integers.

The "infinite loop"  is deliberate, quite like

    ones = 1 : ones

which generates an infinite sequence of 1s.

It is not stated, but the (+) is understood to have been overloaded to handle lists of Nums in the natural way

Doug