-val problem_of: div:(string option) -> conv:string list -> nums:string list -> problem\r
-(* the following will soon replace the one above *)\r
-val problem_of_string_tmp: string -> problem\r
+val problem_of: (string (* problem label *)\r
+* Num.i_var option (* div *)\r
+* Num.i_n_var list (* conv *)\r
+* Num.i_n_var list (* ps *)\r
+* string list (* names of free variables *)) -> problem\r