What is a manipulator?
C++ manipulators are functions or operators that are used specifically with input and output streams in order to manipulate those streams or to insert or extract special characters. Many manipulators apply to both input and output streams but some are specific to one or the other.
The following list briefly describes all the manipulators available in C++, including those only available in C++11. Most manipulators can be found in the <iOS> header, while the parameterised manipulators (those that accept arguments) will be found in the
Output stream manipulators <iOS>
std::flush - synchronises the output buffer with the controlled output sequence
std::endl - inserts a newline character (\n) and flushes the output stream
std::ends - inserts a null character (\0) without flushing the output stream
Input stream manipulators <iOS>
std::ws - extracts and discards whitespace characters from the input stream
Numerical base format manipulators ("basefield" flags) <iOS>
std::dec - inserts/extracts integral numeric data with decimal notation
std::hex - inserts/extracts integral numeric data with hexadecimal notation
std::oct - inserts/extracts integral numeric data with octal notation
Floating-point format manipulators ("floatfield" flags) <iOS>
std::fixed - inserts/extracts floating point values with fixed notation
std::scientific - inserts/extracts floating point values with scientific notation
std::hexfloat - inserts/extracts floating point values with hecadecimal notation (C++11 only)
std::defaultfloat - default behaviour (C++11 only)
Adjustment manipulators ("adjustfield" flags) <iOS>
std::internal - output is padded to the field width by inserting fill characters at a specified internal point
std::left - output is padded to the filed width by appending fill characters
std::right - output is padded to the field width by prepending fill characters
Flags (on) <iOS>
std::boolalpha - generates text values "true" and "false" for boolean values
std::showbase - generates the base for basefield values
std::showpoint - generates a decimal point for "floatfield" values
std::showpos - generates positive sign to positive values
std::skipws - ignores whitespace characters
std::unitbuf - flushes the buffer after every insertion
std::uppercase - generates upper-case letters for generated letters
Flags (off) <iOS>
std::noboolalpha - does not generate text values for boolean values
std::noshowbase - does not generate the base for basefield values
std::noshowpoint - does not generate decimal point for "floatfield" values unless the decimal portion is non-zero
std::noshowpos - does not generate positive sign for positive values
std::noskipws - does not ignore whitespace characters
std::nounitbuf - does not flush the buffer afer every insertion
std::nouppercase - does not generate upper-case letters for generated letters
Parameterised manipulators
std::setiOSflags - set format flags
std::resetiOSflags - reset format flags
std::setbase - set basefield flag
std::setfill - set fill character
std::setprecision - set floatfield precision
std::setw - set field width
Many of these manipulators work together. For instance, the std::internal, std::left and std::rightmanipulators all work in conjunction with the std::setwand std::setfill manipulators.
All manipulators are implemented as operators which can be chained together using the insertion (<<) or extraction (>>) operators as appropriate to the stream. Excluding the parameterised manipulators, most manipulators are also implemented as functions (passing the streram as an argument). Others, including all parameterised manipulators, are implemented as members of the stream. Some, such as std::flush, are implemented all three ways; as an operator, a function and a member function.
Some examples of manipulator usage:
// set field width to 8 characters for console output
std::cout << std::setw (8); // operator
std::cout.width (8); // member method
// set precision to 16 places for floatfields
std::cout << std::setprecision (16); // operator
std::cout.precision (16); // member method
// insert newline and flush stream
std::cout << std::endl; // operator
std::endl (std::cout); // function
// flush stream
std::cout << std::flush; // operator
std::flush (std::cout); // function
std::cout.flush (); // member method
// generate hexadecimal values with base prefix
std::cout << std::showbase << std::hex; // operator
std::showbase (std::cout); // function
std::hex (std::cout); // function
More information on manipulators can be found in the sources and related links section, below.
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