| Defined in header <cfenv> | ||||
|---|---|---|---|---|
| (since C++11) |
The macro constant FE_DFL_ENV expands to an expression of type const std::fenv_t*, which points to a full copy of the default floating-point environment, that is, the environment as loaded at program startup.
Additional macros that begin with FE_ followed by uppercase letters, and have the type const std::fenv_t*, may be supported by an implementation.
Example
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 | #include <iostream>#include <cfenv> #pragma STDC FENV_ACCESS ON void show_env(){ int e = std::fetestexcept(FE_ALL_EXCEPT); if(e & FE_DIVBYZERO) std::cout << "division by zero is raised\n"; if(e & FE_INEXACT) std::cout << "inexact is raised\n"; if(e & FE_INVALID) std::cout << "invalid is raised\n"; if(e & FE_UNDERFLOW) std::cout << "underflow is raised\n"; if(e & FE_OVERFLOW) std::cout << "overflow is raised\n"; int r = std::fegetround(); switch(r) { case FE_DOWNWARD: std::cout << "rounding down\n"; break; case FE_TONEAREST: std::cout << "rounding to nearest\n"; break; case FE_TOWARDZERO: std::cout << "rounding to zero\n"; break; case FE_UPWARD: std::cout << "rounding up\n"; break; }} int main(){ std::cout << "On startup: \n"; show_env(); std::feraiseexcept(FE_UNDERFLOW | FE_OVERFLOW); std::fesetround(FE_UPWARD); std::cout << "\nBefore restoration: \n"; show_env(); std::fesetenv(FE_DFL_ENV); std::cout << "\nAfter reset to default: \n"; show_env();} |
Output:
1 2 3 4 5 6 7 8 9 10 | On startup: rounding to nearest Before restoration: underflow is raisedoverflow is raisedrounding up After reset to default: rounding to nearest |
See also
| (C++11) | saves or restores the current floating point environment (function) |
| (C++11) | restores the floating-point environment and raises the previously raise exceptions (function) |
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