[complex.numbers]

# 29 Numerics library [[numerics]](./#numerics)

## 29.4 Complex numbers [complex.numbers]

### [29.4.1](#general) General [[complex.numbers.general]](complex.numbers.general)

[1](#general-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L180)

The header [<complex>](#header:%3ccomplex%3e "29.4.2 Header <complex> synopsis [complex.syn]") defines a class template,
and numerous functions for representing and manipulating complex numbers[.](#general-1.sentence-1)

[2](#general-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L184)

The effect of instantiating the primary template of complex for any type
that is not a cv-unqualified floating-point type ([[basic.fundamental]](basic.fundamental "6.9.2 Fundamental types"))
is unspecified[.](#general-2.sentence-1)

Specializations of complex for cv-unqualified floating-point types
are trivially copyable literal types ([[basic.types.general]](basic.types.general#term.literal.type "6.9.1 General"))[.](#general-2.sentence-2)

[3](#general-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L191)

If the result of a function is not mathematically defined or not in
the range of representable values for its type, the behavior is
undefined[.](#general-3.sentence-1)

[4](#general-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L196)

If z is an lvalue of type cv complex<T> then:

- [(4.1)](#general-4.1)

the expression reinterpret_cast<cv T(&)[2]>(z) is well-formed,

- [(4.2)](#general-4.2)

reinterpret_cast<cv T(&)[2]>(z)[0] designates the real part of z, and

- [(4.3)](#general-4.3)

reinterpret_cast<cv T(&)[2]>(z)[1] designates the imaginary part of z[.](#general-4.sentence-1)

Moreover, if a is an expression of type cv complex<T>* and the expression a[i] is well-defined for an integer expression i, then:

- [(4.4)](#general-4.4)

reinterpret_cast<cv T*>(a)[2 * i] designates the real part of a[i], and

- [(4.5)](#general-4.5)

reinterpret_cast<cv T*>(a)[2 * i + 1] designates the imaginary part of a[i][.](#general-4.sentence-2)

### [29.4.2](#complex.syn) Header <complex> synopsis [[complex.syn]](complex.syn)

[🔗](#header:%3ccomplex%3e)

namespace std {// [[complex]](#complex "29.4.3 Class template complex"), class template complextemplate<class T> class complex; // [[complex.ops]](#complex.ops "29.4.6 Non-member operations"), operatorstemplate<class T> constexpr complex<T> operator+(const complex<T>&, const complex<T>&); template<class T> constexpr complex<T> operator+(const complex<T>&, const T&); template<class T> constexpr complex<T> operator+(const T&, const complex<T>&); template<class T> constexpr complex<T> operator-(const complex<T>&, const complex<T>&); template<class T> constexpr complex<T> operator-(const complex<T>&, const T&); template<class T> constexpr complex<T> operator-(const T&, const complex<T>&); template<class T> constexpr complex<T> operator*(const complex<T>&, const complex<T>&); template<class T> constexpr complex<T> operator*(const complex<T>&, const T&); template<class T> constexpr complex<T> operator*(const T&, const complex<T>&); template<class T> constexpr complex<T> operator/(const complex<T>&, const complex<T>&); template<class T> constexpr complex<T> operator/(const complex<T>&, const T&); template<class T> constexpr complex<T> operator/(const T&, const complex<T>&); template<class T> constexpr complex<T> operator+(const complex<T>&); template<class T> constexpr complex<T> operator-(const complex<T>&); template<class T> constexpr bool operator==(const complex<T>&, const complex<T>&); template<class T> constexpr bool operator==(const complex<T>&, const T&); template<class T, class charT, class traits> basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>&, complex<T>&); template<class T, class charT, class traits> basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>&, const complex<T>&); // [[complex.value.ops]](#complex.value.ops "29.4.7 Value operations"), valuestemplate<class T> constexpr T real(const complex<T>&); template<class T> constexpr T imag(const complex<T>&); template<class T> constexpr T abs(const complex<T>&); template<class T> constexpr T arg(const complex<T>&); template<class T> constexpr T norm(const complex<T>&); template<class T> constexpr complex<T> conj(const complex<T>&); template<class T> constexpr complex<T> proj(const complex<T>&); template<class T> constexpr complex<T> polar(const T&, const T& = T()); // [[complex.transcendentals]](#complex.transcendentals "29.4.8 Transcendentals"), transcendentalstemplate<class T> constexpr complex<T> acos(const complex<T>&); template<class T> constexpr complex<T> asin(const complex<T>&); template<class T> constexpr complex<T> atan(const complex<T>&); template<class T> constexpr complex<T> acosh(const complex<T>&); template<class T> constexpr complex<T> asinh(const complex<T>&); template<class T> constexpr complex<T> atanh(const complex<T>&); template<class T> constexpr complex<T> cos (const complex<T>&); template<class T> constexpr complex<T> cosh (const complex<T>&); template<class T> constexpr complex<T> exp (const complex<T>&); template<class T> constexpr complex<T> log (const complex<T>&); template<class T> constexpr complex<T> log10(const complex<T>&); template<class T> constexpr complex<T> pow (const complex<T>&, const T&); template<class T> constexpr complex<T> pow (const complex<T>&, const complex<T>&); template<class T> constexpr complex<T> pow (const T&, const complex<T>&); template<class T> constexpr complex<T> sin (const complex<T>&); template<class T> constexpr complex<T> sinh (const complex<T>&); template<class T> constexpr complex<T> sqrt (const complex<T>&); template<class T> constexpr complex<T> tan (const complex<T>&); template<class T> constexpr complex<T> tanh (const complex<T>&); // [[complex.tuple]](#complex.tuple "29.4.9 Tuple interface"), tuple interfacetemplate<class T> struct tuple_size; template<size_t I, class T> struct tuple_element; template<class T> struct tuple_size<complex<T>>; template<size_t I, class T> struct tuple_element<I, complex<T>>; template<size_t I, class T>constexpr T& get(complex<T>&) noexcept; template<size_t I, class T>constexpr T&& get(complex<T>&&) noexcept; template<size_t I, class T>constexpr const T& get(const complex<T>&) noexcept; template<size_t I, class T>constexpr const T&& get(const complex<T>&&) noexcept; // [[complex.literals]](#complex.literals "29.4.11 Suffixes for complex number literals"), complex literalsinline namespace literals {inline namespace complex_literals {constexpr complex<long double> operator""il(long double); constexpr complex<long double> operator""il(unsigned long long); constexpr complex<double> operator""i(long double); constexpr complex<double> operator""i(unsigned long long); constexpr complex<float> operator""if(long double); constexpr complex<float> operator""if(unsigned long long); }}}

### [29.4.3](#complex) Class template complex [[complex]](complex)

[🔗](#lib:complex)

namespace std {template<class T> class complex {public:using value_type = T; constexpr complex(const T& re = T(), const T& im = T()); constexpr complex(const complex&) = default; template<class X> constexpr explicit(*see below*) complex(const complex<X>&); constexpr T real() const; constexpr void real(T); constexpr T imag() const; constexpr void imag(T); constexpr complex& operator= (const T&); constexpr complex& operator+=(const T&); constexpr complex& operator-=(const T&); constexpr complex& operator*=(const T&); constexpr complex& operator/=(const T&); constexpr complex& operator=(const complex&); template<class X> constexpr complex& operator= (const complex<X>&); template<class X> constexpr complex& operator+=(const complex<X>&); template<class X> constexpr complex& operator-=(const complex<X>&); template<class X> constexpr complex& operator*=(const complex<X>&); template<class X> constexpr complex& operator/=(const complex<X>&); };}

[1](#complex-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L347)

The classcomplex describes an object that can
store the Cartesian components,real() andimag(),
of a complex
number[.](#complex-1.sentence-1)

### [29.4.4](#complex.members) Member functions [[complex.members]](complex.members)

[🔗](#lib:complex,constructor)

`constexpr complex(const T& re = T(), const T& im = T());
`

[1](#complex.members-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L366)

*Postconditions*: real() == re && imag() == im is true[.](#complex.members-1.sentence-1)

[🔗](#lib:complex,constructor_)

`template<class X> constexpr explicit(see below) complex(const complex<X>& other);
`

[2](#complex.members-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L377)

*Effects*: Initializes the real part with other.real() and
the imaginary part with other.imag()[.](#complex.members-2.sentence-1)

[3](#complex.members-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L382)

*Remarks*: The expression inside explicit evaluates to false if and only if the floating-point conversion rank of T is greater than or equal to the floating-point conversion rank of X[.](#complex.members-3.sentence-1)

[🔗](#lib:real,complex)

`constexpr T real() const;
`

[4](#complex.members-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L395)

*Returns*: The value of the real component[.](#complex.members-4.sentence-1)

[🔗](#lib:real,complex_)

`constexpr void real(T val);
`

[5](#complex.members-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L406)

*Effects*: Assigns val to the real component[.](#complex.members-5.sentence-1)

[🔗](#lib:imag,complex)

`constexpr T imag() const;
`

[6](#complex.members-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L417)

*Returns*: The value of the imaginary component[.](#complex.members-6.sentence-1)

[🔗](#lib:imag,complex_)

`constexpr void imag(T val);
`

[7](#complex.members-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L428)

*Effects*: Assigns val to the imaginary component[.](#complex.members-7.sentence-1)

### [29.4.5](#complex.member.ops) Member operators [[complex.member.ops]](complex.member.ops)

[🔗](#lib:operator+=,complex)

`constexpr complex& operator+=(const T& rhs);
`

[1](#complex.member.ops-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L441)

*Effects*: Adds the scalar value rhs to the real part of the complex value*this and stores the result in the real part of*this,
leaving the imaginary part unchanged[.](#complex.member.ops-1.sentence-1)

[2](#complex.member.ops-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L449)

*Returns*: *this[.](#complex.member.ops-2.sentence-1)

[🔗](#lib:operator-=,complex)

`constexpr complex& operator-=(const T& rhs);
`

[3](#complex.member.ops-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L460)

*Effects*: Subtracts the scalar value rhs from the real part of the complex value*this and stores the result in the real part of*this,
leaving the imaginary part unchanged[.](#complex.member.ops-3.sentence-1)

[4](#complex.member.ops-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L468)

*Returns*: *this[.](#complex.member.ops-4.sentence-1)

[🔗](#lib:operator*=,complex)

`constexpr complex& operator*=(const T& rhs);
`

[5](#complex.member.ops-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L479)

*Effects*: Multiplies the scalar value rhs by the complex value*this and stores the result in*this[.](#complex.member.ops-5.sentence-1)

[6](#complex.member.ops-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L486)

*Returns*: *this[.](#complex.member.ops-6.sentence-1)

[🔗](#lib:operator/=,complex)

`constexpr complex& operator/=(const T& rhs);
`

[7](#complex.member.ops-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L497)

*Effects*: Divides the scalar value rhs into the complex value*this and stores the result in*this[.](#complex.member.ops-7.sentence-1)

[8](#complex.member.ops-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L504)

*Returns*: *this[.](#complex.member.ops-8.sentence-1)

[🔗](#lib:operator=,complex)

`template<class X> constexpr complex& operator=(const complex<X>& rhs);
`

[9](#complex.member.ops-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L515)

*Effects*: Assigns the value rhs.real() to the real part and
the value rhs.imag() to the imaginary part
of the complex value *this[.](#complex.member.ops-9.sentence-1)

[10](#complex.member.ops-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L521)

*Returns*: *this[.](#complex.member.ops-10.sentence-1)

[🔗](#lib:operator+=,complex_)

`template<class X> constexpr complex& operator+=(const complex<X>& rhs);
`

[11](#complex.member.ops-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L532)

*Effects*: Adds the complex value rhs to the complex value*this and stores the sum in*this[.](#complex.member.ops-11.sentence-1)

[12](#complex.member.ops-12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L539)

*Returns*: *this[.](#complex.member.ops-12.sentence-1)

[🔗](#lib:operator-=,complex_)

`template<class X> constexpr complex& operator-=(const complex<X>& rhs);
`

[13](#complex.member.ops-13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L550)

*Effects*: Subtracts the complex value rhs from the complex value*this and stores the difference in*this[.](#complex.member.ops-13.sentence-1)

[14](#complex.member.ops-14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L557)

*Returns*: *this[.](#complex.member.ops-14.sentence-1)

[🔗](#lib:operator*=,complex_)

`template<class X> constexpr complex& operator*=(const complex<X>& rhs);
`

[15](#complex.member.ops-15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L568)

*Effects*: Multiplies the complex value rhs by the complex value*this and stores the product in*this[.](#complex.member.ops-15.sentence-1)

[16](#complex.member.ops-16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L575)

*Returns*: *this[.](#complex.member.ops-16.sentence-1)

[🔗](#lib:operator/=,complex_)

`template<class X> constexpr complex& operator/=(const complex<X>& rhs);
`

[17](#complex.member.ops-17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L586)

*Effects*: Divides the complex value rhs into the complex value*this and stores the quotient in*this[.](#complex.member.ops-17.sentence-1)

[18](#complex.member.ops-18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L593)

*Returns*: *this[.](#complex.member.ops-18.sentence-1)

### [29.4.6](#complex.ops) Non-member operations [[complex.ops]](complex.ops)

[🔗](#lib:operator+,complex)

`template<class T> constexpr complex<T> operator+(const complex<T>& lhs);
`

[1](#complex.ops-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L606)

*Returns*: complex<T>(lhs)[.](#complex.ops-1.sentence-1)

[🔗](#complex.ops-itemdecl:2)

`template<class T> constexpr complex<T> operator+(const complex<T>& lhs, const complex<T>& rhs);
template<class T> constexpr complex<T> operator+(const complex<T>& lhs, const T& rhs);
template<class T> constexpr complex<T> operator+(const T& lhs, const complex<T>& rhs);
`

[2](#complex.ops-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L618)

*Returns*: complex<T>(lhs) += rhs[.](#complex.ops-2.sentence-1)

[🔗](#lib:operator-,complex)

`template<class T> constexpr complex<T> operator-(const complex<T>& lhs);
`

[3](#complex.ops-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L629)

*Returns*: complex<T>(-lhs.real(),-lhs.imag())[.](#complex.ops-3.sentence-1)

[🔗](#lib:operator-,complex_)

`template<class T> constexpr complex<T> operator-(const complex<T>& lhs, const complex<T>& rhs);
template<class T> constexpr complex<T> operator-(const complex<T>& lhs, const T& rhs);
template<class T> constexpr complex<T> operator-(const T& lhs, const complex<T>& rhs);
`

[4](#complex.ops-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L642)

*Returns*: complex<T>(lhs) -= rhs[.](#complex.ops-4.sentence-1)

[🔗](#lib:operator*,complex)

`template<class T> constexpr complex<T> operator*(const complex<T>& lhs, const complex<T>& rhs);
template<class T> constexpr complex<T> operator*(const complex<T>& lhs, const T& rhs);
template<class T> constexpr complex<T> operator*(const T& lhs, const complex<T>& rhs);
`

[5](#complex.ops-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L655)

*Returns*: complex<T>(lhs) *= rhs[.](#complex.ops-5.sentence-1)

[🔗](#lib:operator/,complex)

`template<class T> constexpr complex<T> operator/(const complex<T>& lhs, const complex<T>& rhs);
template<class T> constexpr complex<T> operator/(const complex<T>& lhs, const T& rhs);
template<class T> constexpr complex<T> operator/(const T& lhs, const complex<T>& rhs);
`

[6](#complex.ops-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L668)

*Returns*: complex<T>(lhs) /= rhs[.](#complex.ops-6.sentence-1)

[🔗](#lib:operator==,complex)

`template<class T> constexpr bool operator==(const complex<T>& lhs, const complex<T>& rhs);
template<class T> constexpr bool operator==(const complex<T>& lhs, const T& rhs);
`

[7](#complex.ops-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L680)

*Returns*: lhs.real() == rhs.real() && lhs.imag() == rhs.imag()[.](#complex.ops-7.sentence-1)

[8](#complex.ops-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L684)

*Remarks*: The imaginary part is assumed to beT(),
or 0.0, for theT arguments[.](#complex.ops-8.sentence-1)

[🔗](#lib:operator%3e%3e,complex)

`template<class T, class charT, class traits>
  basic_istream<charT, traits>& operator>>(basic_istream<charT, traits>& is, complex<T>& x);
`

[9](#complex.ops-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L700)

*Preconditions*: The input values are convertible toT[.](#complex.ops-9.sentence-1)

[10](#complex.ops-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L705)

*Effects*: Extracts a complex number x of the form:u,(u),
or(u,v),
whereu is the real part andv is the imaginary part ([[istream.formatted]](istream.formatted "31.7.5.3 Formatted input functions"))[.](#complex.ops-10.sentence-1)

[11](#complex.ops-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L718)

If bad input is encountered, callsis.setstate(ios_base​::​failbit) (which may throwios_base​::​​failure ([[iostate.flags]](iostate.flags "31.5.4.4 Flags functions")))[.](#complex.ops-11.sentence-1)

[12](#complex.ops-12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L724)

*Returns*: is[.](#complex.ops-12.sentence-1)

[13](#complex.ops-13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L728)

*Remarks*: This extraction is performed as a series of simpler
extractions[.](#complex.ops-13.sentence-1)

Therefore, the skipping of whitespace is specified to be
the same for each of the simpler extractions[.](#complex.ops-13.sentence-2)

[🔗](#lib:operator%3c%3c,complex)

`template<class T, class charT, class traits>
  basic_ostream<charT, traits>& operator<<(basic_ostream<charT, traits>& o, const complex<T>& x);
`

[14](#complex.ops-14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L743)

*Effects*: Inserts the complex number x onto the stream o as if it were implemented as follows:basic_ostringstream<charT, traits> s;
s.flags(o.flags());
s.imbue(o.getloc());
s.precision(o.precision());
s << '(' << x.real() << ',' << x.imag() << ')';return o << s.str();

[15](#complex.ops-15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L756)

[*Note [1](#complex.ops-note-1)*:

In a locale in which comma is used as a decimal point character, the
use of comma as a field separator can be ambiguous[.](#complex.ops-15.sentence-1)

Insertingshowpoint into the output stream forces all outputs to
show an explicit decimal point character; as a result, all inserted sequences of
complex numbers can be extracted unambiguously[.](#complex.ops-15.sentence-2)

— *end note*]

### [29.4.7](#complex.value.ops) Value operations [[complex.value.ops]](complex.value.ops)

[🔗](#lib:real,complex__)

`template<class T> constexpr T real(const complex<T>& x);
`

[1](#complex.value.ops-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L774)

*Returns*: x.real()[.](#complex.value.ops-1.sentence-1)

[🔗](#lib:imag,complex__)

`template<class T> constexpr T imag(const complex<T>& x);
`

[2](#complex.value.ops-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L785)

*Returns*: x.imag()[.](#complex.value.ops-2.sentence-1)

[🔗](#lib:abs,complex)

`template<class T> constexpr T abs(const complex<T>& x);
`

[3](#complex.value.ops-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L796)

*Returns*: The magnitude of x[.](#complex.value.ops-3.sentence-1)

[🔗](#lib:arg,complex)

`template<class T> constexpr T arg(const complex<T>& x);
`

[4](#complex.value.ops-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L807)

*Returns*: The phase angle of x, or atan2(imag(x), real(x))[.](#complex.value.ops-4.sentence-1)

[🔗](#lib:norm,complex)

`template<class T> constexpr T norm(const complex<T>& x);
`

[5](#complex.value.ops-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L818)

*Returns*: The squared magnitude of x[.](#complex.value.ops-5.sentence-1)

[🔗](#lib:conj,complex)

`template<class T> constexpr complex<T> conj(const complex<T>& x);
`

[6](#complex.value.ops-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L829)

*Returns*: The complex conjugate of x[.](#complex.value.ops-6.sentence-1)

[🔗](#lib:proj,complex)

`template<class T> constexpr complex<T> proj(const complex<T>& x);
`

[7](#complex.value.ops-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L840)

*Returns*: The projection of x onto the Riemann sphere[.](#complex.value.ops-7.sentence-1)

[8](#complex.value.ops-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L844)

*Remarks*: Behaves the same as the C function cproj[.](#complex.value.ops-8.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.9.5

[🔗](#lib:polar,complex)

`template<class T> constexpr complex<T> polar(const T& rho, const T& theta = T());
`

[9](#complex.value.ops-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L856)

*Preconditions*: rho is non-negative and non-NaN[.](#complex.value.ops-9.sentence-1)

theta is finite[.](#complex.value.ops-9.sentence-2)

[10](#complex.value.ops-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L860)

*Returns*: Thecomplex value corresponding
to a complex number whose magnitude is rho and whose phase angle
is theta[.](#complex.value.ops-10.sentence-1)

### [29.4.8](#complex.transcendentals) Transcendentals [[complex.transcendentals]](complex.transcendentals)

[🔗](#lib:acos,complex)

`template<class T> constexpr complex<T> acos(const complex<T>& x);
`

[1](#complex.transcendentals-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L878)

*Returns*: The complex arc cosine of x[.](#complex.transcendentals-1.sentence-1)

[2](#complex.transcendentals-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L882)

*Remarks*: Behaves the same as the C function cacos[.](#complex.transcendentals-2.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.5.1

[🔗](#lib:asin,complex)

`template<class T> constexpr complex<T> asin(const complex<T>& x);
`

[3](#complex.transcendentals-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L895)

*Returns*: The complex arc sine of x[.](#complex.transcendentals-3.sentence-1)

[4](#complex.transcendentals-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L899)

*Remarks*: Behaves the same as the C function casin[.](#complex.transcendentals-4.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.5.2

[🔗](#lib:atan,complex)

`template<class T> constexpr complex<T> atan(const complex<T>& x);
`

[5](#complex.transcendentals-5)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L912)

*Returns*: The complex arc tangent of x[.](#complex.transcendentals-5.sentence-1)

[6](#complex.transcendentals-6)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L916)

*Remarks*: Behaves the same as the C function catan[.](#complex.transcendentals-6.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.5.3

[🔗](#lib:acosh,complex)

`template<class T> constexpr complex<T> acosh(const complex<T>& x);
`

[7](#complex.transcendentals-7)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L929)

*Returns*: The complex arc hyperbolic cosine of x[.](#complex.transcendentals-7.sentence-1)

[8](#complex.transcendentals-8)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L933)

*Remarks*: Behaves the same as the C function cacosh[.](#complex.transcendentals-8.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.6.1

[🔗](#lib:asinh,complex)

`template<class T> constexpr complex<T> asinh(const complex<T>& x);
`

[9](#complex.transcendentals-9)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L946)

*Returns*: The complex arc hyperbolic sine of x[.](#complex.transcendentals-9.sentence-1)

[10](#complex.transcendentals-10)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L950)

*Remarks*: Behaves the same as the C function casinh[.](#complex.transcendentals-10.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.6.2

[🔗](#lib:atanh,complex)

`template<class T> constexpr complex<T> atanh(const complex<T>& x);
`

[11](#complex.transcendentals-11)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L963)

*Returns*: The complex arc hyperbolic tangent of x[.](#complex.transcendentals-11.sentence-1)

[12](#complex.transcendentals-12)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L967)

*Remarks*: Behaves the same as the C function catanh[.](#complex.transcendentals-12.sentence-1)

See also: ISO/IEC 9899:2024, 7.3.6.3

[🔗](#lib:cos,complex)

`template<class T> constexpr complex<T> cos(const complex<T>& x);
`

[13](#complex.transcendentals-13)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L979)

*Returns*: The complex cosine of x[.](#complex.transcendentals-13.sentence-1)

[🔗](#lib:cosh,complex)

`template<class T> constexpr complex<T> cosh(const complex<T>& x);
`

[14](#complex.transcendentals-14)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L990)

*Returns*: The complex hyperbolic cosine of x[.](#complex.transcendentals-14.sentence-1)

[🔗](#lib:exp,complex)

`template<class T> constexpr complex<T> exp(const complex<T>& x);
`

[15](#complex.transcendentals-15)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1001)

*Returns*: The complex base-e exponential of x[.](#complex.transcendentals-15.sentence-1)

[🔗](#lib:log,complex)

`template<class T> constexpr complex<T> log(const complex<T>& x);
`

[16](#complex.transcendentals-16)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1012)

*Returns*: The complex natural (base-e) logarithm of x[.](#complex.transcendentals-16.sentence-1)

For all x,imag(log(x)) lies in the interval [−π, π][.](#complex.transcendentals-16.sentence-2)

[*Note [1](#complex.transcendentals-note-1)*:

The semantics of this function are intended to be the same in C++
as they are for clog in C[.](#complex.transcendentals-16.sentence-3)

— *end note*]

[17](#complex.transcendentals-17)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1021)

*Remarks*: The branch cuts are along the negative real axis[.](#complex.transcendentals-17.sentence-1)

[🔗](#lib:log10,complex)

`template<class T> constexpr complex<T> log10(const complex<T>& x);
`

[18](#complex.transcendentals-18)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1032)

*Returns*: The complex common (base-10) logarithm of x, defined aslog(x) / log(10)[.](#complex.transcendentals-18.sentence-1)

[19](#complex.transcendentals-19)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1037)

*Remarks*: The branch cuts are along the negative real axis[.](#complex.transcendentals-19.sentence-1)

[🔗](#lib:pow,complex)

`template<class T> constexpr complex<T> pow(const complex<T>& x, const complex<T>& y);
template<class T> constexpr complex<T> pow(const complex<T>& x, const T& y);
template<class T> constexpr complex<T> pow(const T& x, const complex<T>& y);
`

[20](#complex.transcendentals-20)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1050)

*Returns*: The complex power of base x raised to the yth power,
defined asexp(y * log(x))[.](#complex.transcendentals-20.sentence-1)

The value returned forpow(0, 0) is implementation-defined[.](#complex.transcendentals-20.sentence-2)

[21](#complex.transcendentals-21)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1059)

*Remarks*: The branch cuts are along the negative real axis[.](#complex.transcendentals-21.sentence-1)

[🔗](#lib:sin,complex)

`template<class T> constexpr complex<T> sin(const complex<T>& x);
`

[22](#complex.transcendentals-22)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1070)

*Returns*: The complex sine of x[.](#complex.transcendentals-22.sentence-1)

[🔗](#lib:sinh,complex)

`template<class T> constexpr complex<T> sinh(const complex<T>& x);
`

[23](#complex.transcendentals-23)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1081)

*Returns*: The complex hyperbolic sine of x[.](#complex.transcendentals-23.sentence-1)

[🔗](#lib:sqrt,complex)

`template<class T> constexpr complex<T> sqrt(const complex<T>& x);
`

[24](#complex.transcendentals-24)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1092)

*Returns*: The complex square root of x, in the range of the right
half-plane[.](#complex.transcendentals-24.sentence-1)

[*Note [2](#complex.transcendentals-note-2)*:

The semantics of this function are intended to be the same in C++
as they are for csqrt in C[.](#complex.transcendentals-24.sentence-2)

— *end note*]

[25](#complex.transcendentals-25)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1101)

*Remarks*: The branch cuts are along the negative real axis[.](#complex.transcendentals-25.sentence-1)

[🔗](#lib:tan,complex)

`template<class T> constexpr complex<T> tan(const complex<T>& x);
`

[26](#complex.transcendentals-26)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1112)

*Returns*: The complex tangent of x[.](#complex.transcendentals-26.sentence-1)

[🔗](#lib:tanh,complex)

`template<class T> constexpr complex<T> tanh(const complex<T>& x);
`

[27](#complex.transcendentals-27)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1123)

*Returns*: The complex hyperbolic tangent of x[.](#complex.transcendentals-27.sentence-1)

### [29.4.9](#complex.tuple) Tuple interface [[complex.tuple]](complex.tuple)

[🔗](#lib:tuple_size)

`template<class T>
struct tuple_size<complex<T>> : integral_constant<size_t, 2> {};

template<size_t I, class T>
struct tuple_element<I, complex<T>> {
  using type = T;
};
`

[1](#complex.tuple-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1143)

*Mandates*: I < 2 is true[.](#complex.tuple-1.sentence-1)

[🔗](#lib:get,complex)

`template<size_t I, class T>
  constexpr T& get(complex<T>& z) noexcept;
template<size_t I, class T>
  constexpr T&& get(complex<T>&& z) noexcept;
template<size_t I, class T>
  constexpr const T& get(const complex<T>& z) noexcept;
template<size_t I, class T>
  constexpr const T&& get(const complex<T>&& z) noexcept;
`

[2](#complex.tuple-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1161)

*Mandates*: I < 2 is true[.](#complex.tuple-2.sentence-1)

[3](#complex.tuple-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1165)

*Returns*: A reference to the real part of z if I == 0 is true,
otherwise a reference to the imaginary part of z[.](#complex.tuple-3.sentence-1)

### [29.4.10](#cmplx.over) Additional overloads [[cmplx.over]](cmplx.over)

[1](#cmplx.over-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1173)

The following function templates have additional constexpr overloads:arg norm
conj proj
imag real

[2](#cmplx.over-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1186)

The additional constexpr overloads are sufficient to ensure:

- [(2.1)](#cmplx.over-2.1)

  If the argument has a floating-point type T,
then it is effectively cast to complex<T>[.](#cmplx.over-2.1.sentence-1)

- [(2.2)](#cmplx.over-2.2)

  Otherwise, if the argument has integer type,
then it is effectively cast to complex<double>[.](#cmplx.over-2.2.sentence-1)

[3](#cmplx.over-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1198)

Function template pow has additional constexpr overloads sufficient to ensure,
for a call with one argument of type complex<T1> and
the other argument of type T2 or complex<T2>,
both arguments are effectively cast to complex<common_type_t<T1, T3>>,
where T3 isdouble if T2 is an integer type and T2 otherwise[.](#cmplx.over-3.sentence-1)

If common_type_t<T1, T3> is not well-formed,
then the program is ill-formed[.](#cmplx.over-3.sentence-2)

### [29.4.11](#complex.literals) Suffixes for complex number literals [[complex.literals]](complex.literals)

[1](#complex.literals-1)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1212)

This subclause describes literal suffixes for constructing complex number literals[.](#complex.literals-1.sentence-1)

The suffixes i, il, and if create complex numbers of
the types complex<double>, complex<long double>, andcomplex<float> respectively, with their imaginary part denoted by the
given literal number and the real part being zero[.](#complex.literals-1.sentence-2)

[🔗](#lib:operator%22%22il,complex)

`constexpr complex<long double> operator""il(long double d);
constexpr complex<long double> operator""il(unsigned long long d);
`

[2](#complex.literals-2)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1226)

*Returns*: complex<long double>{0.0L, static_cast<long double>(d)}[.](#complex.literals-2.sentence-1)

[🔗](#lib:operator%22%22i,complex)

`constexpr complex<double> operator""i(long double d);
constexpr complex<double> operator""i(unsigned long long d);
`

[3](#complex.literals-3)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1238)

*Returns*: complex<double>{0.0, static_cast<double>(d)}[.](#complex.literals-3.sentence-1)

[🔗](#lib:operator%22%22if,complex)

`constexpr complex<float> operator""if(long double d);
constexpr complex<float> operator""if(unsigned long long d);
`

[4](#complex.literals-4)

[#](http://github.com/Eelis/draft/tree/9adde4bc1c62ec234483e63ea3b70a59724c745a/source/numerics.tex#L1250)

*Returns*: complex<float>{0.0f, static_cast<float>(d)}[.](#complex.literals-4.sentence-1)