Difference between revisions of "cpp/numeric/fenv/feround"
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| − | 1) Attempts to establish the floating-point rounding direction equal to the | + | 1) Attempts to establish the floating-point rounding direction equal to the argument {{tt|round}}, which is expected to be one of the [[cpp/numeric/fenv/FE_round|floating point rounding macros]]. |
2) Returns the value of the [[cpp/numeric/fenv/FE_round|floating point rounding macro]] that corresponds to the current rounding direction. | 2) Returns the value of the [[cpp/numeric/fenv/FE_round|floating point rounding macro]] that corresponds to the current rounding direction. | ||
Revision as of 13:43, 1 October 2012
Template:ddcl list begin <tr class="t-dsc-header">
<td>Defined in header
</td>
<cfenv>
<td></td> <td></td> </tr> <tr class="t-dcl ">
<td >int fesetround( int round )
</td>
<td > (1) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">
<td >int fegetround()
</td>
<td > (2) </td> <td > (since C++11) </td> </tr> Template:ddcl list end
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 │
