Use the remove/erase idiom: std::vector<int>& vec = myNumbers; // use shorter name vec.erase(std::remove(vec.begin(), vec.end(), number_in), vec.end()); What happens is that remove compacts the elements that differ from the value to be removed (number_in) in the beginning of the vector and returns the iterator to the first element after that range. Then erase removes these elements … Read more
Use std::vector‘s range constructor: std::vector<int> intVec; std::vector<double> doubleVec(intVec.begin(), intVec.end());
No, you can’t. Range-based for is for when you need to access each element of a container once. You should use the normal for loop or one of its cousins if you need to modify the container as you go along, access an element more than once, or otherwise iterate in a non-linear fashion through … Read more
std::array is just a class version of the classic C array. That means its size is fixed at compile time and it will be allocated as a single chunk (e.g. taking space on the stack). The advantage it has is slightly better performance because there is no indirection between the object and the arrayed data. … Read more
Why not simply using the variance: var(x) == 0 If all the elements of x are equal, you will get a variance of 0. This works only for double and integers though. Edit based on the comments below: A more generic option would be to check for the length of unique elements in the vector … Read more
Quaternion q; vector a = crossproduct(v1, v2); q.xyz = a; q.w = sqrt((v1.Length ^ 2) * (v2.Length ^ 2)) + dotproduct(v1, v2); Don’t forget to normalize q. Richard is right about there not being a unique rotation, but the above should give the “shortest arc,” which is probably what you need.
In C++, things are passed by value unless you specify otherwise using the &-operator (note that this operator is also used as the ‘address-of’ operator, but in a different context). This is all well documented, but I’ll re-iterate anyway: void foo(vector<int> bar); // by value void foo(vector<int> &bar); // by reference (non-const, so modifiable inside … Read more
You need to make use of the begin and end method of the vector class, which return the iterator referring to the first and the last element respectively. using namespace std; vector<string> myvector; // a vector of stings. // push some strings in the vector. myvector.push_back(“a”); myvector.push_back(“b”); myvector.push_back(“c”); myvector.push_back(“d”); vector<string>::iterator it; // declare an iterator … Read more
This was missed from C++98 standard proper but later added as part of a TR. The forthcoming C++0x standard will of course contain this as a requirement. From n2798 (draft of C++0x): 23.2.6 Class template vector [vector] 1 A vector is a sequence container that supports random access iterators. In addition, it supports (amortized) constant … Read more
arrays: are a builtin language construct; come almost unmodified from C89; provide just a contiguous, indexable sequence of elements; no bells and whistles; are of fixed size; you can’t resize an array in C++ (unless it’s an array of POD and it’s allocated with malloc); their size must be a compile-time constant unless they are … Read more