std:: fegetround, std:: fesetround
From cppreference.com
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Defined in header
<cfenv>
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int
fesetround
(
int
round
)
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(1) | (since C++11) |
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int
fegetround
(
)
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(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.
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.
Notes
The current rounding mode, reflecting the effects of the most recent
fesetround
, can also be queried with
FLT_ROUNDS
.
See floating-point rounding macros for the effects of rounding.
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
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(C++11)
(C++11)
(C++11)
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nearest integer using current rounding mode
(function) |
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(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
(C++11)
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nearest integer using current rounding mode with
exception if the result differs (function) |
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C documentation
for
fegetround
,
fesetround
|
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