Re: 'withing' problem

[tmoran@acm.org]

> The implementation of 'print' would call 'toString(x)' and output the result.
  I thought toString might be intended for that, but then I'd expect it to
return a fixed type like String, not some extendable (ie, variable) type "seq".

> Correct. But the declaration of 'toString' needs to be in the package for
> 'anything', so the package for 'anything' needs to 'with' the package for
> 'seq', and vice versa.
> >   function toString(x:anything'class) return seq;

  If toString takes "anything'class", then it's not a primitive of "anything"
and needn't be declared in the same package as "anything".  In particular,
"toString" and "seq" can be declared together in a package that with's
the package that declares "anything".

package Root_Of_All is
  type anything is tagged null record;
  ...
end Root_Of_All;

with Root_Of_All;
package Debugging_Help is
  type seq is new anything with record
    ...
  end record;
  function toString(x:Root_Of_All.anything'class) return seq;
  -- yields "unprintable object" as seq
  -- Should be overloaded for printable objects
  ...
end Debugging_Help;

with Root_Of_All, Debugging_Help;
package Something is
  type heir is new ... --- descendent of "anything"
  function toString(x:heir'class) return seq;
  -- seq is suitable for printing for debugging or whatever
  ...