Basic question about std::vector instantiation

Posted by recipriversexclusion on Stack Overflow See other posts from Stack Overflow or by recipriversexclusion
Published on 2010-03-13T15:45:55Z Indexed on 2010/03/13 16:05 UTC
Read the original article Hit count: 360

Filed under:

stl

|

stdvector

|

c++

This looks simple but I am confused: The way I create a vector of hundred, say, ints is

std::vector<int>  *pVect = new std::vector<int>(100);

However, looking at std::vector's documentation I see that its constructor is of the form

explicit vector ( size_type n, const T& value= T(), const Allocator& = Allocator() );

So, how does the previous one work? Does new call the constructor with an initialization value obtained from the default constructor? If that is the case, would

std::vector<int, my_allocator> *pVect = new std::vector<int>(100, my_allocator);

where I pass my own allocator, also work?

© Stack Overflow or respective owner

Related posts about stl

Fastest way to write large STL vector to file using STL

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a large vector (10^9 elements) of chars, and I was wondering what is the fastest way to write such vector to a file. So far I've been using next code: vector<char> vs; // ... Fill vector with data ofstream outfile("nanocube.txt", ios::out | ios::binary); ostream_iterator<char>… >>> More
question about STL thread-safe and STL debugging

as seen on Stack Overflow - Search for 'Stack Overflow'
I have two questions about STL 1) why STL is not thread-safe? Is there any structure that is thread-safe? 2) How to debug STL using GDB? In GDB, how can I print a vector? >>> More
The C++ Standard Template Library as a BDB Database (part 1)

as seen on Oracle Blogs - Search for 'Oracle Blogs'
If you've used C++ you undoubtedly have used the Standard Template Libraries. Designed for in-memory management of data and collections of data this is a core aspect of all C++ programs. Berkeley DB is a database library with a variety of APIs designed to ease development, one of those APIs extends… >>> More
Design approach, string table data, variables, stl memory usage

as seen on Stack Overflow - Search for 'Stack Overflow'
I have an old structure class like this: typedef vector<vector<string>> VARTYPE_T; which works as a single variable. This variable can hold from one value over a list to data like a table. Most values are long,double, string or double [3] for coordinates (x,y,z). I just convert them as… >>> More
Sort list using stl sort function

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm trying to sort a list (part of a class) in descending containg items of a struct but it doesn't compile(error: no match for 'operator-' in '__last - __first'): sort(Result.poly.begin(), Result.poly.end(), SortDescending()); And here's SortDescending: struct SortDescending { bool operator()(const… >>> More

Related posts about stdvector

A cross between std::multimap and std::vector?

as seen on Stack Overflow - Search for 'Stack Overflow'
I'm looking for a STL container that works like std::multimap, but has constant access time to random n-th element. I need this because I have such structure in memory that is std::multimap for many reasons, but items stored in it have to be presented to the user in a listbox. Since amount of data… >>> More
no match for operator= using a std::vector

as seen on Stack Overflow - Search for 'Stack Overflow'
I've got a class declared like this: class Level { private: std::vector<mapObject::MapObject> features; (...) }; and in one of its member functions I try to iterate through that vector like this: vector<mapObject::MapObject::iterator it; for(it=features.begin(); it<features… >>> More
Basic question about std::vector instantiation

as seen on Stack Overflow - Search for 'Stack Overflow'
This looks simple but I am confused: The way I create a vector of hundred, say, ints is std::vector<int> *pVect = new std::vector<int>(100); However, looking at std::vector's documentation I see that its constructor is of the form explicit vector ( size_type n, const T& value=… >>> More
Weird behavior of std::vector

as seen on Stack Overflow - Search for 'Stack Overflow'
I have a class like this: class OBJ{...}; class A { public: vector<OBJ> v; A(int SZ){v.clear(); v.reserve(SZ);} }; A *a = new A(123); OBJ something; a->v.push_back(something); This is a simplified version of my code. The problem is in debug mode it works perfect. But in release… >>> More
Putting a C++ Vector as a Member in a Class that Uses a Memory Pool

as seen on Stack Overflow - Search for 'Stack Overflow'
Hey, I've been writing a multi-threaded DLL for database access using ADO/ODBC for use with a legacy application. I need to keep multiple database connections for each thread, so I've put the ADO objects for each connection in an object and thinking of keeping an array of them inside a custom threadInfo… >>> More