Initializing a vector of a vector in a constructor

[fatgirl.brown]

Hi all,

I am attempting to initialize a vector of a vector in a constructor
with some clean-looking syntax and am not sure of how to go about this.
For instance:

double weight;
vector< vector<unsigned> > posInd;

Table() :
weight(0), posInd(???)
{}

Table(const TableEntry& o) :
weight(o.weight), posInd(???)
{}

Table(double weight = 0.0, vector< vector<unsigned> > posInd) :
weight(weight), posInd(???)
{}

Many thanks for your patience!

 

[Nindi73]

Hi all,

I am attempting to initialize a vector of a vector in a constructor
with some clean-looking syntax and am not sure of how to go about this.
For instance:

double weight;
vector< vector<unsigned> > posInd;

Table() :
weight(0), posInd(???)
{}

Table(const TableEntry& o) :
weight(o.weight), posInd(???)
{}

Table(double weight = 0.0, vector< vector<unsigned> > posInd) :
weight(weight), posInd(???)
{}

Many thanks for your patience!

The Syntax is the same as if it were just a vector of PODs.

Table() :
weight(0), posInd(5)
{}


would give you a vector of 5 vectors, BUT each of thos 5 vectors would
be default constructed, if you wanted them all to be sized to a size
other than zero, you have no choice but to resize each of them in the
constructor body, for example in a for loop.
N

 

[Ivan Vecerina]

....
: > vector< vector<unsigned> > posInd;
....
: The Syntax is the same as if it were just a vector of PODs.
:
: Table() :
: weight(0), posInd(5)
: {}
:
:
: would give you a vector of 5 vectors, BUT each of thos 5 vectors would
: be default constructed, if you wanted them all to be sized to a size
: other than zero, you have no choice but to resize each of them in the
: constructor body, for example in a for loop.

Actually, if all second-level vectors are to have the same size,
you can define their size at initialization time:
posInd( sizeX, vector<unsigned>( sizeY, 0 ) )

(where 0 could also be replaced by another value to fill
each cell of the 2D vector with).


hth -Ivan

 

[lscyung]

Great - thanks to the both of you!

 

[Nindi73]

...
: > vector< vector<unsigned> > posInd;
...
: The Syntax is the same as if it were just a vector of PODs.
:
: Table() :
: weight(0), posInd(5)
: {}
:
:
: would give you a vector of 5 vectors, BUT each of thos 5 vectors would
: be default constructed, if you wanted them all to be sized to a size
: other than zero, you have no choice but to resize each of them in the
: constructor body, for example in a for loop.

Actually, if all second-level vectors are to have the same size,
you can define their size at initialization time:
posInd( sizeX, vector<unsigned>( sizeY, 0 ) )

(where 0 could also be replaced by another value to fill
each cell of the 2D vector with).

Your absolutley right !!! I am such a pleb !!!!