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because the argument to f must be a variable integer, but i is a constant integer. This matching is a form of program correctness, and is known as const-correctness.This allows a form of programming by contract, where functions specify as part of their type signature whether they modify their arguments or not, and whether their return value is modifiable or not.
The std::string type is the main string datatype in standard C++ since 1998, but it was not always part of C++. From C, C++ inherited the convention of using null-terminated strings that are handled by a pointer to their first element, and a library of functions that manipulate such strings.
Making a shallow copy of a const or immutable value removes the outer layer of immutability: Copying an immutable string (immutable(char[])) returns a string (immutable(char)[]). The immutable pointer and length are being copied and the copies are mutable.
For example, vfprintf() is an alternate version of fprintf() expecting a va_list instead of the actual unnamed argument list. A user-defined variadic function can therefore initialize a va_list variable using va_start and pass it to an appropriate standard library function, in effect passing the unnamed argument list by reference instead of ...
Examples are if, while, const, for and goto, which are keywords that happen to be common to both languages. In C, the basic built-in type names are also keywords (e.g., int, char) or combinations of keywords (e.g., unsigned char), while in Pascal the built-in type names are predefined normal identifiers.
Each string ends at the first occurrence of the zero code unit of the appropriate kind (char or wchar_t).Consequently, a byte string (char*) can contain non-NUL characters in ASCII or any ASCII extension, but not characters in encodings such as UTF-16 (even though a 16-bit code unit might be nonzero, its high or low byte might be zero).
The type of the first string is the usual const char[]. The type of the second string is const char16_t[] (note lower case 'u' prefix). The type of the third string is const char32_t[] (upper case 'U' prefix). When building Unicode string literals, it is often useful to insert Unicode code points directly into the string. To do this, C++11 ...
But it comes with a performance penalty for string literals, as std::string usually allocates memory dynamically, and must copy the C-style string literal to it at run time. Before C++11, there was no literal for C++ strings (C++11 allows "this is a C++ string"s with the s at the end of the literal), so the normal constructor syntax was used ...