The hash function is responsible for the unordered associative containers’ constant access time (best cast). As ever, C++ offers many ways to adjust the behavior of the hash functions. On the one hand, C++ has a lot of different hash functions; on the other hand, you can define your hash function. You can even adjust […]
Before I take a deeper look insight the interface of the hash tables – officially called unordered associative containers – I will first compare the performance of the associative containers. The best candidates are std::unordered_map and the ordered pendant std::map because both are used most frequently.
We missed the hash table in C++ for a long time. They promise to have constant access time. C++11 has hash tables in four variations. The official name is unordered associative containers. Unofficially, they are called dictionaries or just simple associative arrays.
If you look carefully, you see type-traits have a big optimization potential. The type-traits support the first step to analyze the code at the compile-time and, in the second step, to optimize the code based on that analysis. How is that possible? Dependent on the type of variable, a faster variant of an algorithm will […]
constexpr functions are functions that can be executed at compile time. Sounds not so thrilling. But it is. Trust me. You can perform with constexpr functions a lot of calculations at compile time. Therefore, the calculation result is at runtime as a constant in ROM available. In addition, constexpr functions are implicitly inline.
If you declare a variable as constexpr the compiler will evaluate them at compile time. This holds not only true for built-in types but also for instantiations of user-defined types. There are a few serious restrictions for objects to evaluate at compile time.
You can define with the keyword constexpr an expression that can be evaluated at compile time. constexpr can be used for variables, functions, and user-defined types. An expression that is evaluated at compile time has a lot of advantages. For example, constexpr variables and instances of user-defined types are automatically thread-safe and can be stored […]
Thanks to inline, the compiler can replace the function call with the function body. There are two reasons to use inline functions: performance and safety.
The new null pointer nullptr cleans up in C++ with the ambiguity of 0 and the macro NULL.
Using the context-sensitive keyword override and final, you can explicitly manage the overriding of virtual functions. In particular, the keyword override solves many issues with difficulty finding bugs in object hierarchies: Methods that should override methods of base classes. The result is syntactically but not a semantically correct program. The program performs the wrong stuff […]