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From: "Matthew Heaney" <mheaney@on2.com>
Newsgroups: comp.lang.lisp,comp.lang.ada,comp.lang.eiffel,comp.lang.smalltalk
Subject: Re: True faiths ( was Re: The true faith )
Date: Fri, 18 Jan 2002 18:53:32 -0500
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"Richard Riehle" <richard@adaworks.com> wrote in message
news:3C48AE35.BA38ED04@adaworks.com...
> In C++ or Ada (or whatever) there is no need to write an assignment
> operator unless the assignment between two objects is more complex
> than predefined assignment.    One benefit of the limited type in Ada is
> to highlight the dangers of assignment.   This is also why most complex
> data structures in Ada are limited types.

That's why I routinely turn off copy-assignment and copy-construction in my
ADTs:

class C
{
public:
   C();
   //...
private:
   C& operator=(const C&);
   C(const C&);
  //...
};

I recently had to override assignment for a type, but that was only for a
class sans vtable (the type wasn't "tagged").  Fortunately, I haven't had to
overrided assignment for a tagged type.


> This specification makes clear the contract and still eliminates any
> possibility for stupid assignment between objects of the type.

What I showed above is the standard C++ idiom for doing the same.