Difference between revisions of "cpp/numeric/fenv/feround"
From cppreference.com
(+summary) |
m (Use since= and until= params of {{dcl}} template.) |
||
| Line 3: | Line 3: | ||
{{dcl begin}} | {{dcl begin}} | ||
{{dcl header | cfenv}} | {{dcl header | cfenv}} | ||
| − | {{dcl | | + | {{dcl | since=c++11 | num=1| |
int fesetround( int round ) | int fesetround( int round ) | ||
}} | }} | ||
| − | {{dcl | | + | {{dcl | since=c++11 | num=2| |
int fegetround() | int fegetround() | ||
}} | }} | ||
Revision as of 15:42, 1 July 2013
| Defined in header <cfenv>
|
||
| int fesetround( int round ) |
(1) | (since C++11) |
| int fegetround() |
(2) | (since C++11) |
Manages the floating-point rounding direction.
1) Attempts to establish the floating-point rounding direction equal to the argument
round, which is expected to be one of the floating point rounding macros. 2) Returns the value of the floating point rounding macro that corresponds to the current rounding direction.
Contents |
Parameters
| round | - | rounding direction, one of floating point rounding macros |
Return value
1) 0 on success, non-zero otherwise.
2) the floating point rounding macro describing the current rounding direction or a negative value if the direction cannot be determined
Example
Run this code
#include <cfenv> #include <cmath> #include <iomanip> #include <iostream> #include <utility> // #pragma STDC FENV_ACCESS ON int main() { static constexpr std::pair<const char*, const double> samples[] { {" 12.0", 12.0}, {" 12.1", 12.1}, {"-12.1", -12.1}, {" 12.5", 12.5}, {"-12.5", -12.5}, {" 12.9", 12.9}, {"-12.9", -12.9}, {" 13.0", 13.0} }; std::cout << "│ sample │ FE_DOWNWARD │ FE_UPWARD │ FE_TONEAREST │ FE_TOWARDZERO │\n"; for (const auto& [str, fp] : samples) { std::cout << "│ " << std::setw(6) << str << " │ "; for (const int dir : {FE_DOWNWARD, FE_UPWARD, FE_TONEAREST, FE_TOWARDZERO}) { std::fesetround(dir); std::cout << std::setw(10) << std::fixed << std::nearbyint(fp) << " │ "; } std::cout << '\n'; } }
Output:
│ sample │ FE_DOWNWARD │ FE_UPWARD │ FE_TONEAREST │ FE_TOWARDZERO │ │ 12.0 │ 12.000000 │ 12.000000 │ 12.000000 │ 12.000000 │ │ 12.1 │ 12.000000 │ 13.000000 │ 12.000000 │ 12.000000 │ │ -12.1 │ -13.000000 │ -12.000000 │ -12.000000 │ -12.000000 │ │ 12.5 │ 12.000000 │ 13.000000 │ 12.000000 │ 12.000000 │ │ -12.5 │ -13.000000 │ -12.000000 │ -12.000000 │ -12.000000 │ │ 12.9 │ 12.000000 │ 13.000000 │ 13.000000 │ 12.000000 │ │ -12.9 │ -13.000000 │ -12.000000 │ -13.000000 │ -12.000000 │ │ 13.0 │ 13.000000 │ 13.000000 │ 13.000000 │ 13.000000 │
See also
| (C++11)(C++11)(C++11) |
nearest integer using current rounding mode (function) |
| (C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11) |
nearest integer using current rounding mode with exception if the result differs (function) |
