I was reading Bjarne Stroustrup's Programming Principles and Practice Using C (second edition). On page 597:
double* p5 = new double[] {0,1,2,3,4};
...; the number of elements can be left out when a set of elements is provided.
I typed the code above into Visual Studio 2022, and I get red underlines saying that "incomplete type is not allowed" (same thing happens when I define p5 as a data member), nevertheless, the code compiles and runs successfully.
May I ask if it is fine to define array in such way? If so, why would Visual Studio show those red underlines...?
CodePudding user response：
May I ask if it is fine to define array in such way?
Yes, starting from C 11 it is valid. From new expression's documentation:
double* p = new double[]{1,2,3}; // creates an array of type double[3]
This means in your example:
double* p5 = new double[] {0,1,2,3,4};
creates an array of type double[5]
Note
This was proposed in p1009r2.
CodePudding user response：
If it has to be on the heap then use
std::vector<double> v{0, 1, 2, 3, 4};
if it can be on the stack then use
std::array a{0., 1., 2., 3., 4.}; // all elements must have the right type
std::array b(std::to_array<double>({1, 2, 3})); // when conversion is easier than typing fully typed objects