function template
<complex>
std::abs
template<class T> T abs (const complex<T>& x);
Complex number's absolute value
Returns the absolute value of the complex number x.
The absolute value of a complex number is its magnitude (or modulus), defined as the theoretical distance between the coordinates (real,imag) of x and (0,0) (applying the Pythagorean theorem).
This function is overloaded in <cstdlib> for integral types (see cstdlib abs), in <cmath> for floating-point types (see cmath abs), and in <valarray> for valarrays (see valarray abs).
返回值
The absolute value of x.
T 是 complex 类型的分量类型（即其值类型）。
示例
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// abs complex example
#include <iostream> // std::cout
#include <complex> // std::complex, std::abs
int main ()
{
std::complex<double> mycomplex (3.0,4.0);
std::cout << "The absolute value of " << mycomplex << " is " << std::abs(mycomplex) << '\n';
return 0;
}
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输出
The absolute value of (3,4) is 5
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