Re: Wide_Text_IO: bad data in text file

["Grein, Christoph" <christoph.grein@eurocopter.com>]

> The RM doesn't specifically address this issue, as far as I can tell. 
> Data_Error seems to be intended for cases where characters can be read
> from the file but they're not in the proper syntax for an integer
> (when using an instance of Integer_IO), or a float, or whatever.  The
> closest thing I could find was A.13(10), which says "Use_Error is
> propagated if an operation is attempted that is not possible for
> reasons that depend on characteristics of the external file".  When I
> tried a test using GNAT, it raised Constraint_Error, which seems
> counterintuitive.

Exactly when did Gnat raise Constraint_Error? At the Get? Or later when you use the value 
read?

My interpretation of the RM is that Data_Error should be raised, however it need 
not be raised if this would be too much of a burden (cannot be easily done). If 
Data_Error is not raised, you have invalid data.

The 'Valid attribute can be used to insure that the data read really is valid 
(i.e. has a legal interpretation). This attribute is there for just this 
purpose.