File positions.
module Biocaml_pos: sigtype |    | file :  | (* | file name | *) | 
|    | line :  | (* | line number | *) | 
|    | col :  | (* | column number, can be defined only if line number is too | *) | 
exception Bad of string
exception Undefined
val flc : string -> int -> int -> tf stands for file name, l for
    line number, and c for column number. The arguments required
    correspond to the function name. There is no fc nor c function
    because a line number is required when a column number is given.val col_exn : t -> intBiocaml_pos.Undefined if given position does not have requested information.val set_col : t -> int -> tBad if
    resulting t would be ill-formed.val to_string : t -> stringinclude Core.Sexpable.S
end