Re: OOD in Ada?

[tmoran@acm.org]

> ... build my class heierarchy all deriving from a single base class
> ... Note that this pretty much circumvents any type safety ...
  I can't phrase it well, but this bother me.  In parsing, you have a
bunch of terminals and non-terminals and a base non-terminal (something
like "program").  So make a base class of Non_Terminal with children like
"Declarative_Part", "Expression", "Term", etc.  That's the general
paradigm for a parser.
  Then you have a particular grammar that says that an Expression can have
a Statement as a constituent (in the OP's case), or that a Term can be
followed by an Adding_Operator, and so forth.  It seems to me overdoing
things to try to use the Ada type system to encode particular syntax
rules, especially when you consider that a particular grammar may change
due to changes in the language, or to arrange to call semantic routines at
more convenient times, or whatever.