Floating-point environment(since C++11)

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Ranges library(C++20)
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Numerics library

Common mathematical functions

Mathematical special functions(C++17)

Mathematical constants(C++20)

Basic linear algebra algorithms(C++26)

Data-parallel types (SIMD)(C++26)

Floating-point environment(C++11)

Complex numbers

Numeric array (valarray)

Pseudo-random number generation

Bit manipulation(C++20)

Saturation arithmetic(C++26)

(C++17)

(C++17)

(C++20)

(C++20)

Generic numeric operations

iota (C++11)
ranges::iota (C++23)
accumulate
inner_product
adjacent_difference
partial_sum

reduce (C++17)
transform_reduce (C++17)
inclusive_scan (C++17)
exclusive_scan (C++17)
transform_inclusive_scan (C++17)
transform_exclusive_scan (C++17)

C-style checked integer arithmetic

ckd_add (C++26)
ckd_sub (C++26)

ckd_mul (C++26)

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Floating-point environment

Functions
feclearexcept (C++11)
fetestexcept (C++11)
feraiseexcept (C++11)
fegetexceptflagfesetexceptflag (C++11)(C++11)
fegetroundfesetround (C++11)(C++11)
fegetenvfesetenv (C++11)(C++11)
feholdexcept (C++11)
feupdateenv (C++11)
Macro constants
FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C++11)(C++11)(C++11)(C++11)(C++11)(C++11)
FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C++11)(C++11)(C++11)(C++11)
FE_DFL_ENV (C++11)

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The floating-point environment is the set of floating-point status flags and control modes supported by the implementation. It is thread-local. Each thread inherits the initial state of its floating-point environment from the parent thread. Floating-point operations modify the floating-point status flags to indicate abnormal results or auxiliary information. The state of floating-point control modes affects the outcomes of some floating-point operations.

The floating-point environment access and modification is only meaningful when#pragma STDC FENV_ACCESS is supported and is set toON. Otherwise the implementation is free to assume that floating-point control modes are always the default ones and that floating-point status flags are never tested or modified. In practice, few current compilers, such as HP aCC, Oracle Studio, or IBM XL, support the#pragma explicitly, but most compilers allow meaningful access to the floating-point environment anyway.

[edit]Types

Defined in header`<cfenv>`
fenv_t (C++11)	the type representing the entire floating-point environment (typedef)[edit]
fexcept_t (C++11)	the type representing all floating-point status flags collectively (typedef)[edit]

[edit]Functions

feclearexcept (C++11)	clears the specified floating-point status flags (function)[edit]
fetestexcept (C++11)	determines which of the specified floating-point status flags are set (function)[edit]
feraiseexcept (C++11)	raises the specified floating-point exceptions (function)[edit]
fegetexceptflagfesetexceptflag (C++11)(C++11)	copies the state of the specified floating-point status flags from or to the floating-point environment (function)[edit]
fegetroundfesetround (C++11)(C++11)	gets or sets rounding direction (function)[edit]
fegetenvfesetenv (C++11)	saves or restores the current floating-point environment (function)[edit]
feholdexcept (C++11)	saves the environment, clears all status flags and ignores all future errors (function)[edit]
feupdateenv (C++11)	restores the floating-point environment and raises the previously raised exceptions (function)[edit]

[edit]Macros

FE_ALL_EXCEPTFE_DIVBYZEROFE_INEXACTFE_INVALIDFE_OVERFLOWFE_UNDERFLOW (C++11)	floating-point exceptions (macro constant)[edit]
FE_DOWNWARDFE_TONEARESTFE_TOWARDZEROFE_UPWARD (C++11)	floating-point rounding direction (macro constant)[edit]
FE_DFL_ENV (C++11)	default floating-point environment (macro constant)[edit]

[edit]Notes

The floating-point exceptions are not related to the C++ exceptions. When a floating-point operation raises a floating-point exception, the status of the floating-point environment changes, which can be tested withstd::fetestexcept, but the execution of a C++ program on most implementations continues uninterrupted.

There are compiler extensions that may be used to generate C++ exceptions automatically whenever a floating-point exception is raised:

GNU libc functionfeenableexcept() enables trapping of the floating-point exceptions, which generates the signalSIGFPE. If the compiler option-fnon-call-exceptions was used, the handler for that signal may throw a user-defined C++ exception.
MSVC function_control87() enables trapping of the floating-point exceptions, which generates a hardware exception, which can be converted to C++ exceptions with_set_se_translator.