Re: S-expression I/O in Ada

[Simon Wright <simon@pushface.org>]

I'd disagree with Jeffrey here.

Nothing wrong with stating at the bottom! especially when you already
know that the component you're looking at is likely to be useful and to
fit into *your* way of thinking about things. Your plan already has
higher-level abstractions, so that if you get to the next layer up and
want to change your lowest layer (if only for experimentation's sake)
you will be able to do so.

Lots of people round here are responsible for component libraries at
various levels of abstraction which they've developed for their own
purposes and then pushed out to the community in the hope they'll help
someone else.

The only caution I'd add is that, at some point, when you're reading an
S-expression from an external file and you expect the next 4 bytes to
contain an integer in binary little-endian format, you're going to have
to trust _something_ to have got it right; if you wrote "*(struct foo
**)((char *)whatever + bar.offset)" in C you will have to write the
equivalent in Ada. Unless you were going to invent a sort of checked
S-expression? (I don't get that impression!)

--S