Defined in header `<cmath>` | ||
---|---|---|

float trunc ( float arg ); float truncf( float arg ); | (1) | (since C++11) |

double trunc ( double arg ); | (2) | (since C++11) |

long double trunc ( long double arg ); long double truncl( long double arg ); | (3) | (since C++11) |

double trunc ( IntegralType arg ); | (4) | (since C++11) |

1-3) Computes the nearest integer not greater in magnitude than

`arg`

.
4) A set of overloads or a function template accepting an argument of any integral type. Equivalent to 2) (the argument is cast to

`double`

).arg | - | floating point value |

If no errors occur, the nearest integer value not greater in magnitude than `arg`

(in other words, `arg`

rounded towards zero) is returned.

Return value

Argument

Errors are reported as specified in `math_errhandling`

.

If the implementation supports IEEE floating-point arithmetic (IEC 60559),

- The current rounding mode has no effect.
- If
`arg`

is ±∞, it is returned, unmodified - If
`arg`

is ±0, it is returned, unmodified - If arg is NaN, NaN is returned

`FE_INEXACT`

may be (but isn't required to be) raised when truncating a non-integer finite value.

The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (including `std::intmax_t`

), when stored in an integer variable.

The implicit conversion from floating-point to integral types also rounds towards zero, but is limited to the values that can be represented by the target type.

#include <cmath> #include <iostream> int main() { std::cout << std::fixed << "trunc(+2.7) = " << std::trunc(+2.7) << '\n' << "trunc(-2.9) = " << std::trunc(-2.9) << '\n' << "trunc(-0.0) = " << std::trunc(-0.0) << '\n' << "trunc(-Inf) = " << std::trunc(-INFINITY) << '\n'; }

Possible output:

trunc(+2.7) = 2.000000 trunc(-2.9) = -2.000000 trunc(-0.0) = -0.000000 trunc(-Inf) = -inf

(C++11)(C++11) | nearest integer not greater than the given value (function) |

(C++11)(C++11) | nearest integer not less than the given value (function) |

(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11)(C++11) | nearest integer, rounding away from zero in halfway cases (function) |

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