cfenv
这个标头最初在C标准库中作为<fenv.h>...
此标头是浮点环境图书馆。
类型
fenv_t  | The type representing the entire floating-point environment  | 
|---|---|
fexcept_t  | The type representing all floating-point status flags collectively  | 
功能
feclearexcept (C++11)  | clears the specified floating-point status flags (function)  | 
|---|---|
fetestexcept (C++11)  | determines which of the specified floating-point status flags are set (function)  | 
feraiseexcept (C++11)  | raises the specified floating-point exceptions (function)  | 
fegetexceptflagfesetexceptflag (C++11)(C++11)  | copies the state of the specified floating-point status flags from or to the floating-point environment (function)  | 
fegetroundfesetround (C++11)(C++11)  | gets or sets rounding direction (function)  | 
fegetenvfesetenv (C++11)  | saves or restores the current floating point environment (function)  | 
feholdexcept (C++11)  | saves the environment, clears all status flags and ignores all future errors (function)  | 
feupdateenv (C++11)  | restores the floating-point environment and raises the previously raise exceptions (function)  | 
宏
FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C++11)  | floating-point exceptions (macro constant)  | 
|---|---|
FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C++11)  | floating-point rounding direction (macro constant)  | 
FE_DFL_ENV (C++11)  | default floating-point environment (macro constant)  | 
简介
二次
namespace std {
    // types
    typedef /*object type*/ fenv_t;
    typedef /*integer type*/ fexcept_t;
 
    // functions
    int feclearexcept(int except);
    int fegetexceptflag(fexcept_t *pflag, int except);
    int feraiseexcept(int except);
    int fesetexceptflag(const fexcept_t *pflag, int except);
    int fetestexcept(int except);
    int fegetround(void);
    int fesetround(int mode);
    int fegetenv(fenv_t *penv);
    int feholdexcept(fenv_t *penv);
    int fesetenv(const fenv_t *penv);
    int feupdateenv(const fenv_t *penv);
}二次
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