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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.
«FUNCTION» LENGTH(string) or «FUNCTION» BYTE-LENGTH(string) number of characters and number of bytes, respectively COBOL: string length string: a decimal string giving the number of characters Tcl: ≢ string: APL: string.len() Number of bytes Rust [30] string.chars().count() Number of Unicode code points Rust [31]
LLVM-GCC has included this function since version 1.5 in June 2005. [16] In the C++ Standard Library, the bit-array data structure bitset has a count() method that counts the number of bits that are set. In C++20, a new header <bit> was added, containing functions std::popcount and std::has_single_bit, taking arguments of unsigned integer types.
Most of the functions that operate on C strings are declared in the string.h header (cstring in C++), while functions that operate on C wide strings are declared in the wchar.h header (cwchar in C++). These headers also contain declarations of functions used for handling memory buffers; the name is thus something of a misnomer.
The function should simply determine this somehow, the means of which vary. Common conventions include: Use of a printf or scanf-like format string with embedded specifiers that indicate argument types. A sentinel value at the end of the variadic arguments. A count argument indicating the number of variadic arguments.
The format string used in strftime traces back to at least PWB/UNIX 1.0, released in 1977. Its date system command includes various formatting options. [2] [3] In 1989, the ANSI C standard is released including strftime and other date and time functions. [4]
Many instances of the most commonly used garbage-collected type, the string, have a short lifetime, since they are typically intermediate values in string manipulation. A lot of local string usage could be optimized away, but the compiler currently doesn't do it. The reference count of a string is checked before mutating a string.
The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for common tasks such as finding the square root of a number.