initialising a vector

[Nick Keighley]

Hi,

is there a way of initialising a vector in a similar fashion to
initialising an array?

consider:
Shape* triangle = new Triangle ();
Shape* square = new Square ();
Shape* shape_arr [] = {&triangle, &square};

is there some of doing something like this?:
vector<Shape*> shape_vec = {&triangle, &square};

 

[James Daughtry]

How about if you combine the two?

Shape* init[] = {new Triangle, new Square};
vector<Shape*> shape_vec(init, init + 2);

 

[Nick Keighley]

[ initialising a vector from an "preset" array ]

How about if you combine the two?

Shape* init[] = {new Triangle, new Square};
vector<Shape*> shape_vec(init, init + 2);

yes

thanks!

 

[Jeff Flinn]

Hi,

is there a way of initialising a vector in a similar fashion to
initialising an array?

consider:
Shape* triangle = new Triangle ();
Shape* square = new Square ();
Shape* shape_arr [] = {&triangle, &square};

is there some of doing something like this?:
vector<Shape*> shape_vec = {&triangle, &square};

See http://www.boost.org/libs/assign/doc/index.html

which allows you to:

vector<Shape*> shape_vec = List_of(&triangle)(&square};

Jeff Flinn

 

[Panjandrum]

See http://www.boost.org/libs/assign/doc/index.html

which allows you to:

vector<Shape*> shape_vec = List_of(&triangle)(&square};

And what is the advantage compared to James Daughtry's clean and simple
solution?

 

[Jeff Flinn]

And what is the advantage compared to James Daughtry's clean and
simple solution?

Well unless my eyes deceive me, the above is accomplished in a single
statement, which is my understanding as to what the OP desired. Also the
boost assignment library allows use in initializers:

class CompoundShape
{
std::vector<Shape*> mShapes;
public:
CompoundShape()
: mShapes( List_of(new Triangle)(new Square) )
{}
};

Although both 'Shape* init[] = {new Triangle, new Square};' and the above
usage may have exception safety issues. What if either Triangle or Square
constructors throw. I'm not sure if even defining 'std::vector<
boost::shared_ptr<Shape> > mShapes;' is sufficient.

Jeff Flinn

 

[Rene Moehring]

How about if you combine the two?

Shape* init[] = {new Triangle, new Square};

That may leak if one new throws.

 

[Kristo]

class CompoundShape
{
std::vector<Shape*> mShapes;
public:
CompoundShape()
: mShapes( List_of(new Triangle)(new Square) )
{}
};

Although both 'Shape* init[] = {new Triangle, new Square};' and the above
usage may have exception safety issues. What if either Triangle or Square
constructors throw. I'm not sure if even defining 'std::vector<
boost::shared_ptr<Shape> > mShapes;' is sufficient.

A smart pointer (one suitable for use in standard containers) will help
you if one new succeeds and the other throws. If either constructor
can throw, it's up to them to free any memory they allocate, per FAQ
17.4.

Kristo

 

[friedlinguini]

Although both 'Shape* init[] = {new Triangle, new Square};' and the above
usage may have exception safety issues. What if either Triangle or Square
constructors throw. I'm not sure if even defining 'std::vector<
boost::shared_ptr<Shape> > mShapes;' is sufficient.

A smart pointer (one suitable for use in standard containers) will help
you if one new succeeds and the other throws. If either constructor
can throw, it's up to them to free any memory they allocate, per FAQ
17.4.

Just introducing smart pointers does not necessarily solve the leak
problem, though it's a step in the right direction:
http://www.gotw.ca/gotw/056.htm