NAME
    function_exists - find out if a named function is defined in an object and return the object filename.

    SYNOPSIS
    string function_exists(string func, object ob)

    DESCRIPTION
    This function searches for a named function `func' in the specified object `ob'. If it is found, the filename of that object is returned.

    The filename returned is not the same as the string returned by the function `file_name()', it does not have the instance number of the found object suffixed to it.

    If no argument `ob' is given, `this_object()' is used by default.

    NOTA BENE
    It is the filename of the object that contains the function that is returned, not the composite object that might inherit the file that contains the function.

    E.g: if the function is in an object inherited by `ob' the filename of the inherited object.

    BUGS
    Does not find the function "heart_beat".

    SEE ALSO
    inherit_list