13.26 iomanip

13.26 <iomanip>

The <iomanip> header declares several I/O manipulators. An I/O manipulator is a function object that can be used in a sequence of input or output operators to manipulate the I/O stream. The manipulators are simple wrappers for functionality that is available as member functions of the ios_base class, but manipulators are simpler to use in some situations.

For example, to print formatted output, the following two code fragments are equivalent:

 // Using manipulators std::cout << std::setw(16) << std::setprecision(12) << x;     // Without manipulators std::cout.width(16); std::cout.precision(12); std::cout << x; 

At a basic level, manipulators are easy to use. If you want to understand exactly how they work, perhaps to write your own, see Chapter 9 for a thorough discussion of I/O, including manipulators.

The return type of each manipulator is implementation-defined. For the following function descriptions, this type is shown as manip_t .

Use a manipulator by applying it to a streamthat is, out << manip , in which out is an instance of basic_ostream , or in >> manip , in which in is an instance of basic_istream . In the following function descriptions, stream refers to the input or output stream to which the manipulator is being applied.

resetiosflags function

Clears specified flags

---

   manip_t    resetiosflags  (ios_base::fmtflags mask) 

The resetiosflags function clears the flag bits in mask for a stream. In other words, it performs the equivalent of stream .setf(ios_base::fmtflags(0) , mask) .

See Also

setiosflags function, ios_base in <ios>

setbase function

Sets conversion radix

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   manip_t    setbase  (int base) 

The setbase function sets the conversion radix for a stream. In other words, it performs the equivalent of stream .setf( newbase , ios_base::basefield) , in which newbase depends on base , as shown in Table 13-11. Notice that any value of a base other than 8, 10, or 16 is treated the same as .

Table 13-11. Conversion radix

setbase argument	fmtflags equivalent
8	ios_base::oct
10	ios_base::dec
16	ios_base::hex
Anything else

See Also

ios_base in <ios>

setfill function template

Sets pad character

---

 template <typename charT>   manip_t    setfill  (charT c) 

The setfill function template sets the fill character for a stream to c . In other words, it performs the equivalent of stream .fill(c) .

See Also

ios_base in <ios>

setiosflags function

Sets specified flags

---

   manip_t    setiosflags  (ios_base::fmtflags mask) 

The setiosflags function sets the flag bits in mask for a stream. In other words, it performs the equivalent of stream .setf(mask) .

See Also

resetiosflags function, ios_base in <ios>

setprecision function

Sets precision

---

   manip_t    setprecision  (int n) 

The setprecision function template sets the output precision for a stream to n . In other words, it performs the equivalent of stream .precision(n) .

See Also

ios_base in <ios>

setw function

Sets field width

---

   manip_t    setw  (int n) 

The setw function template sets the output field width for a stream to n . In other words, it performs the equivalent of stream .width(n) .

See Also

ios_base in <ios>