Re: [boost] range idea (single)

From: Joe Gottman (jgottman_at_[hidden])
Date: 2005-10-26 19:04:06

"Neal Becker" <ndbecker2_at_[hidden]> wrote in message 
news:djogoc$u8q$1_at_sea.gmane.org...
> Suppose one adopts the range concept.  All algorithms are written to 
> accept
> ranges as arguments.
>
> It is common to want to implement a function F, which operates on one data
> element.  For example:
>
> template<typename T>
> T sqr (T x) { return x * x; }
>
> Also, implement a version that operates on a container.  This could be 
> done
> by defining only the single element version, and a version of transform,
> that operates on ranges.
>
> Here's an interesting idea.  Suppose instead that only the range version 
> of
> F is defined, but a range type is made that encapsulates a single element.
> Again, only 1 version of F needs to be defined.
>
> Here is an outline:
> template<typename T>
> struct Single {
>  typedef T* iterator;
>  typedef const T* const_iterator;
>  typedef size_t size_type;
>  Single (T& _x) : x (_x) {}
>  T& x;
>  size_t size() const { return 1; }
>  iterator begin() { return &x; }
>  const_iterator begin() const { return &x; }
>  iterator end() { return &x+1; }
>  const_iterator end() const { return &x+1; }
> // not complete yet...
> };
>

The one thing I'd be concerned about is slicing.
struct Base {};
struct Derived : public Base {int x; }; // Note that Derived does have data 
members.;

Derived d;
Single<Base> foo(d);

Under these circumstances, does calling foo.end(), which will return an 
address in the middle of d, cause any problems?

Joe Gottman