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Thus on the one hand the input string can be const (since it is not modified by the function), and if the input string is const the return value should be as well – most simply because it might return exactly the input pointer, if the first character is a match – but on the other hand the return value should not be const if the original ...
The length of a string is the number of code units before the zero code unit. [1] The memory occupied by a string is always one more code unit than the length, as space is needed to store the zero terminator. Generally, the term string means a string where the code unit is of type char, which is exactly 8 bits on all modern machines.
A basic_string is guaranteed to be specializable for any type with a char_traits struct to accompany it. As of C++11, only char, wchar_t, char16_t and char32_t specializations are required to be implemented. [16] A basic_string is also a Standard Library container, and thus the Standard Library algorithms can be applied to the code units in ...
Even functions can be const in C++. The meaning here is that only a const function may be called for an object instantiated as const; a const function doesn't change any non-mutable data. C# has both a const and a readonly qualifier; its const is only for compile-time constants, while readonly can be used in constructors and other runtime ...
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.
A string is generally considered as a data type and is often implemented as an array data structure of bytes (or words) that stores a sequence of elements, typically characters, using some character encoding. String may also denote more general arrays or other sequence (or list) data types and structures.
A character constant cannot be empty (i.e. '' is invalid syntax), although a string may be (it still has the null terminating character). Multi-character constants (e.g. 'xy' ) are valid, although rarely useful — they let one store several characters in an integer (e.g. 4 ASCII characters can fit in a 32-bit integer, 8 in a 64-bit one).
This is because string literals have array type, char [n] (C) or const char [n] (C++), which cannot be added; this is not a restriction in most other languages. This is particularly important when used in combination with the C preprocessor, to allow strings to be computed following preprocessing, particularly in macros. [13] As a simple example: