rewrite.hs

-- > toChunks "qwer1234asdf" 5                                                  
-- ["qwer1","234as","df000"]                                                    
                                                                                
toChunks ""  _   = []                                                           
toChunks str len = ch:toChunks str' len                                         
    where (ch, str') = get len str                                              
          get len str = if len==0 then ("", str) else (head:chunk, str')        
              where (head, tail) = pop str                                      
                    (chunk, str') = get (len-1) tail                            
          pop ""     = (fill,"")                                                
          pop (v:vs) = (v,vs)                                                   
          fill = '0'