Re: Potential problem in Builder: invalid object copy

[martin f k. <ma...@ma...>]

also sprach stephan beal <st...@s1...> [2004.06.01.1242 +0200]:
> Builder<AType,BType> bob;
>=20
> CType c;
> AType * a =3D bob.build( c );
>=20
> Doh! Undefined copy behaviour!

a compile time error, right?

> Also, it just occurred to me: all of the copy-based funcs are of
> course going to require that the type be Copyable, which may not
> be the case for some types. Many types which are
> default-constructable are not copyable. zB, singletons come to
> mind. It is also possible that BaseT implements Copyable but SubT
> does not, in which case such a call would fail... luckily, at
> compile time.

yeah, that's fine. if you try to do things with the library that you
should not, two things can happen:

  (a) a compiler error
  (b) a runtime error

(b) should be avoided at all cost. (a) should be promoted.

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(on the statement print "42 monkeys"+"1 snake") btw,
both perl and python get this wrong.
perl gives 43 and python gives "42 monkeys1 snake",
when the answer is clearly "41 monkeys and 1 fat snake".
                                                         -- jim fulton