Question

I’m writing some code against a C++ API that takes vectors of vectors of vectors, and it’s getting tedious to write code like the following all over the place:

vector<string> vs1; vs1.push_back('x'); vs1.push_back('y'); ... vector<string> vs2; ... vector<vector<string> > vvs1; vvs1.push_back(vs1); vvs1.push_back(vs2); ... vector<vector<string> > vvs2; ... vector<vector<vector<string> > > vvvs; vvvs.push_back(vvs1); vvvs.push_back(vvs2); ... 

Does C++ have a vector literal syntax? I.e., something like:

vector<vector<vector<string>>> vvvs =      { { {'x','y', ... }, ... }, ... } 

Is there a non-builtin way to accomplish this?

Answer 1

In C++0x you will be able to use your desired syntax:

vector<vector<vector<string> > > vvvs =      { { {'x','y', ... }, ... }, ... }; 

But in today’s C++ you are limited to using boost.assign which lets you do:

vector<string> vs1; vs1 += 'x', 'y', ...; vector<string> vs2; ... vector<vector<string> > vvs1; vvs1 += vs1, vs2, ...; vector<vector<string> > vvs2; ... vector<vector<vector<string> > > vvvs; vvvs += vvs1, vvs2, ...; 

… or using Qt’s containers which let you do it in one go:

QVector<QVector<QVector<string> > > vvvs =     QVector<QVector<QVector<string> > >() << (         QVector<QVector<string> >() << (             QVector<string>() << 'x', 'y', ...) <<             ... ) <<         ...     ; 

The other semi-sane option, at least for flat vectors, is to construct from an array:

string a[] = { 'x', 'y', 'z' }; vector<string> vec(a, a + 3);