Member canvas_print (canvas *c): lze jako makro pomoci canvas_output()
Member concat (char *str,...): pokud str==NULL vracime ""?
Member deleni (int a, int b, int *r): FIXME nefunguje pro zaporna cisla!!!
Member flushget (): zamontovat do cti_int()!? zahodit vstup pokud scanf()==0 ?
Member spojeni (char *t1, char *t2): co kdyz t1, t2 NULL?