Re: In Plain Text: Tags.Internal_Tag(String'Input(Stream)) ??

[tmoran@acm.org]

>This suggests that I have to define my own S'Class'Input()
>instead. This would allow me to read the tag in, in any way I
>please, but then how do I proceed from there? How does the
>Ada S'Class'Input() dispatch once the external tag is known?
  It calls A'Input() if the data indicated type A, or B'Input() if
the data indicated type B, etc.
  So if you can use
     for A'External_Tag use "RIFF";
statements to cover all your tags, you needn't override S'Class'Input.
If your external way of specifying a type is too complex for that,
you will have to override S'Class'Input, and your code will have to
know about all the possible external tags and it will have to call
A'Input() or B'Input() or C'Input() as needed.
  Quite independently, if the external data organization doesn't
happen to match what your compiler expects, say because bounds are
stored differently, you'll have to override A'Input et al.
  As has been pointed out, "For elementary types, the representation
in terms of stream elements is implementation defined."  You may
be unpleasantly surprised.  The order of calls for a composite type
is specified though, so if you write overrides for all the elementary
types, and any composite types that differ in data layout order,
you should be in good shape.