Re: Data table text I/O package?

[Robert A Duff <bobduff@shell01.TheWorld.com>]

Marius Amado Alves <amado.alves@netcabo.pt> writes:

> Yes. This is interesting, useful, and easy. From the header you get the
> field names, from the first data line with deduce the data types. With
> these elements you can generate the record type and procedures to read
> the file.

Hmm.  Interesting idea.  But you will lose the full power of Ada's type
system.  You cannot, in general, deduce the type from the data, in Ada.
I mean, 123 could be any integer type, and a typical Ada program has
many integer types.

For that matter, how do you know 123 is not intended to be Type_String,
in your example below?

>... A trick I often use to deduce data types is based on 'Value:

I believe this trick will run afoul of RM-11.6.  It probably works in
practise, but I think that an implementation is allowed to return
Type_Float, no matter what string you pass to Value!

Did I mention that I don't like 11.6?  ;-)

> function Get_Type (Value : String) return Data_Type is
>     F : Float;
>     I : Integer;
> begin
>     F := Float'Value (Value);
>     return Type_Float;
> exception
>     when Constraint_Error =>
>        begin
>           I := Integer'Value (Value);
>           return Type_Integer;
>        exception
>           when Constraint_Error =>
>              return Type_String;
>        end;
> end;

- Bob