A new writeup on Non-Virtual Interface (NVI) idiom has been written on More C++ Idioms wikibook. In the writeup, I discuss the relationship of NVI with the Fragile Base Class (FBC) problem, which can silently break perfectly good derived classes because of some innocuous changes in the base class.
What new can be said about multi-dimensional arrays in C++? As it turns out, quite a bit! With the advent of C++11, we get new standard library class std::array. We also get new language features, such as template aliases and variadic templates. So I'll talk about interesting ways in which they come together.
It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array?
int native[3][4];
std::array<std::array<int, 3>, 4> arr;
No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is:
std::array<std::array<int, 4>, 3> arr;
That's quite annoying for two r…
It all started with a simple question of how to define a multi-dimensional std::array. It is a great example of deceptively simple things. Are the following the two arrays identical except that one is native and the other one is std::array?
int native[3][4];
std::array<std::array<int, 3>, 4> arr;
No! They are not. In fact, arr is more like an int[4][3]. Note the difference in the array subscripts. The native array is an array of 3 elements where every element is itself an array of 4 integers. 3 rows and 4 columns. If you want a std::array with the same layout, what you really need is:
std::array<std::array<int, 4>, 3> arr;
That's quite annoying for two r…
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