[LC++]STL Iterators and integers

[Mark Phillips]

Grzegorz Mazur wrote:

> > Yes this is okay for my example, but I am
> > wanting something which will work more
> > generally.  I tried a variant on your approach
> > based on a class:
>
> What kind of generality does the above example lack?

You may have a class that contains, as part of it, a vector
of strings,  but also has other things associated with it.
The "array of strings" approach isn't general enough
because it isn't a class.  What would be nice is a class
constructor which can take a hardwired list of strings
as an argument.  One way would be to create a hardwired
array of strings, and then pass this array variable into
the constructor.  But this is a two-step process with an
unnecessary variable declaration --- it would be much
cleaner and nicer if this could be done in a single
hard-wired step.

> > class wiseSayingsTy: public vector<string> {
> > public:
> >   wiseSayingsTy(): vector<string>() {}
> >   wiseSayingsTy(uint N, char const* initList[]): vector<string>() {
> >     for (int i=0; i<N; i++)
> >       push_back(initList[i]);
> >   }
> > };
>
> I'm quite sure, that similar (at least functionally) constructor is
> already defined for vectors. So there is no point in defining it once
> again. And deriving from vector is not the best idea anyway.

I have been hoping this functionality was possible, but
have not yet discovered how to do it.  The docs for vector
list the following constructors:

vector()                         Creates an empty vector.

vector(size_type n)              Creates a vector with n elements.

vector(size_type n, const T& t)  Creates a vector with n copies of t.

vector(const vector&)            The copy constructor.

template <class InputIterator>
vector(InputIterator, InputIterator) Creates a vector with a copy of a range.

This last one is the only one I have had any hope
might do what I want.  But I didn't think it did.
However, your comment:

> std::size_t no_saings = sizeof sayings / sizeof sayings[0];
>
> This way you have all the necessary information to create a pair of
> iterators giving you full power of STL.

leads me to wonder whether maybe there is a way!
But I haven't worked out how yet.

Regarding your comment that deriving from vector
is not the best idea...

Perhaps you're right, but I'm not convinced of this.
If a vector with extra functionality is what you
want, then I don't see why you shouldn't do this.
Also, the C++ programming books I have,
"Thinking in C++", volumes I and II, by Bruce
Eckel, say that  inheriting from STL classes _is_
often a good idea as it means you can use STL
algorithms on the derived classes.  Perhaps there
are good reasons not to inherit a vector, but I
haven't come across any yet.

> > Then I hoped I could write:
> >
> >   wiseSayingsTy wiseSayings(4, {"eat more chocolate", "smell the roses",
> >     "laugh a little", "keep it simple"});
>
> Perhaps a book covering some C++ basics would help?

The Bruce Eckel books have been very helpful.  I haven't
yet come across any way of doing something like the
above, but I am still hopeful that maybe there is a way.

Cheers,

Mark.