std::fixed, std::scientific, std::hexfloat, std::defaultfloat
From cppreference.com
| Defined in header <ios>
|
||
std::ios_base& fixed( std::ios_base& str );
|
(1) | |
std::ios_base& scientific( std::ios_base& str );
|
(2) | |
std::ios_base& hexfloat( std::ios_base& str );
|
(3) | (since C++11) |
std::ios_base& defaultfloat( std::ios_base& str );
|
(4) | (since C++11) |
Modifies the default formatting for floating-point output.
1) Sets the
floatfield of the stream str to fixed as if by calling str.setf(std::ios_base::fixed, std::ios_base::floatfield).2) Sets the
floatfield of the stream str to scientific as if by calling str.setf(std::ios_base::scientific, std::ios_base::floatfield).3) Sets the
floatfield of the stream str to fixed and scientific simultaneously as if by calling str.setf(std::ios_base::fixed | std::ios_base::scientific, std::ios_base::floatfield). This enables hexadecimal floating-point formatting.4) Sets the
floatfield of the stream str to zero, as if by calling str.unsetf(std::ios_base::floatfield). This enables the default floating-point formatting, which is different from fixed and scientific.This is an I/O manipulator, it may be called with an expression such as out << std::fixed for any out of type std::basic_ostream (or with an expression such as in >> std::scientific for any in of type std::basic_istream).
Parameters
| str | - | reference to I/O stream |
Return value
str (reference to the stream after manipulation).
Notes
Hexadecimal floating-point formatting ignores the stream precision specification, as required by the specification of std::num_put::do_put.
These manipulators do not affect floating-point parsing.
Example
Run this code
#include <iomanip>
#include <iostream>
#include <sstream>
enum class cap { title, middle, end };
void print(const char* text, double num, cap c)
{
if (c == cap::title)
std::cout <<
"ββββββββββββ¬βββββββββββββ¬βββββββββββββββββββββββββββ\n"
"β number β iomanip β representation β\n"
"ββββββββββββΌβββββββββββββΌβββββββββββββββββββββββββββ€\n";
std::cout << std::left
<< "β " << std::setw(8) << text << " β fixed β "
<< std::setw(24) << std::fixed << num << " β\n"
<< "β " << std::setw(8) << text << " β scientific β "
<< std::setw(24) << std::scientific << num << " β\n"
<< "β " << std::setw(8) << text << " β hexfloat β "
<< std::setw(24) << std::hexfloat << num << " β\n"
<< "β " << std::setw(8) << text << " β default β "
<< std::setw(24) << std::defaultfloat << num << " β\n";
std::cout << (c != cap::end ?
"ββββββββββββΌβββββββββββββΌβββββββββββββββββββββββββββ€\n" :
"ββββββββββββ΄βββββββββββββ΄βββββββββββββββββββββββββββ\n");
}
int main()
{
print("0.0", 0.0, cap::title);
print("0.01", 0.01, cap::middle);
print("0.00001", 0.00001, cap::end);
// Note; choose clang for correct output
double f;
std::istringstream("0x1.8p+0") >> f;
std::cout << "Parsing 0x1.8p+0 gives " << f << '\n';
std::istringstream("0x1P-1022") >> f;
std::cout << "Parsing 0x1P-1022 gives " << f << '\n';
}
Output:
ββββββββββββ¬βββββββββββββ¬βββββββββββββββββββββββββββ
β number β iomanip β representation β
ββββββββββββΌβββββββββββββΌβββββββββββββββββββββββββββ€
β 0.0 β fixed β 0.000000 β
β 0.0 β scientific β 0.000000e+00 β
β 0.0 β hexfloat β 0x0p+0 β
β 0.0 β default β 0 β
ββββββββββββΌβββββββββββββΌβββββββββββββββββββββββββββ€
β 0.01 β fixed β 0.010000 β
β 0.01 β scientific β 1.000000e-02 β
β 0.01 β hexfloat β 0x1.47ae147ae147bp-7 β
β 0.01 β default β 0.01 β
ββββββββββββΌβββββββββββββΌβββββββββββββββββββββββββββ€
β 0.00001 β fixed β 0.000010 β
β 0.00001 β scientific β 1.000000e-05 β
β 0.00001 β hexfloat β 0x1.4f8b588e368f1p-17 β
β 0.00001 β default β 1e-05 β
ββββββββββββ΄βββββββββββββ΄βββββββββββββββββββββββββββ
Parsing 0x1.8p+0 gives 1.5
Parsing 0x1P-1022 gives 2.22507e-308
See also
| changes floating-point precision (function) |