Re: Q: unboxed values and polymorphism

[dewar@cs.nyu.edu (Robert Dewar)]

Hannes asks

"I'm new to Ada and have a questions on polymorphism. The standard
way to have polymorphism in Ada are tagged records. But for my needs
this requires too much space. List cells would have a size of 3 words
instead of 2. I'd also have to put integers in records. This would
require too much time and space. I'd like to convert access values to
integers and do my own tagging. I could simply translate my C code.
But it would be nice to see how an experienced Ada programmer would do
this in Ada. Can I find some code that does this somewhere ?"

Use variant records. This is a very standard technique which you can
find described in any standard Ada text book, I would recommend
Barnes. Translating your C code would surely result in a horrible
montrosity! No respectable Ada programmers would convert access
values to integers except for very special low level purposes.