real and i
Real numbers are represented in C++ as floating point variables (
float, double, and
long double). The theory of complex numbers defines a superset of real numbers called complex numbers. A complex number is a composite number that consists of two units. The first one is called the
real part and is denoted by a lowercase
r. The unit part is the
imaginary part and is denoted by a lowercase
i. Just as the fractional part and the integral part of the number 10.34 make a single real number, the real and imaginary units are construed as a single complex number. A common way of representing a complex number is to pack two floating point variables in a struct. Problems start when you need to perform mathematical operations on such objects. The built-in operators of C++ +,-,/, etc. do not support an arbitrary user-defined complex number. Using complex numbers in C++ presents two problems:
- The representation of a complex number
- Arithmetic operations such as addition, multiplication, and division of complex numbers
The Standard Library header
<complex> contains a mini-library for manipulating complex numbers easily. It includes the class template
std::complex<T> which has three
explicit specializations, one for every native floating type:
- std::complex<float>
- std::complex<double>
- std::complex<long double>
First, decide which of these three specializations suits your needs best.
std::complex<float> is the most compact, occupying eight bytes per one complex number. Alas, it also has the lowest precision and cannot represent real or imaginary values that are higher than
numeric_limits<float>::max().
std::complex<double> is a reasonable compromise between space usage (16 bytes per object) and precision.
std::complex<long double> offers the highest precision but also uses 20 bytes (at least) per complex number.
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