Editing Operators in C and C++ (section)

===Relational===

All [[Relational operator|relational]] (comparison) operators can be overloaded in C++. Since [[C++20]], the inequality operator is automatically generated if <code>operator==</code> is defined and all four relational operators are automatically generated if <code>operator<=></code> is defined.<ref>{{cite web|url=https://en.cppreference.com/w/cpp/language/operators#Comparison_operators|title=Operator overloading§Comparison operators|website=cppreference.com}}</ref>

{| class="wikitable" style="width:100%"
! colspan="2" rowspan="2" | Operation 
! rowspan="2" | Syntax 
! rowspan="2" | In C
! colspan="2" | C++ prototype
|-
! in class K
! outside class
|-
| {{rh}} colspan="2" | Equal to 
| align="center" | <code>a '''==''' b</code>
| {{yes}}
| {{cpp|1=bool K::operator ==(S const& b) const;}}
| {{cpp|1=bool operator ==(K const& a, S const& b);}}
|-
| {{rh}} colspan="2" | Not equal to 
| style="text-align:center;" | <code>a '''!=''' b</code> || {{yes}}
| {{cpp|1=bool K::operator !=(S const& b) const;}}
| {{cpp|1=bool operator !=(K const& a, S const& b);}}
|- 
| {{rh}} colspan="2" | Greater than 
| style="text-align:center;" | <code>a '''>''' b</code> || {{yes}} 
| {{cpp|1=bool K::operator >(S const& b) const;}}
| {{cpp|1=bool operator >(K const& a, S const& b);}}
|-
| {{rh}} colspan="2" | Less than 
| style="text-align:center;" | <code>a '''<''' b</code> || {{yes}} 
| {{cpp|1=bool K::operator <(S const& b) const;}}
| {{cpp|1=bool operator <(K const& a, S const& b);}}
|-
| {{rh}} colspan="2" | Greater than or equal to 
| style="text-align:center;" | <code>a '''>=''' b</code> || {{yes}} 
| {{cpp|1=bool K::operator >=(S const& b) const;}}
| {{cpp|1=bool operator >=(K const& a, S const& b);}}
|-
| {{rh}} colspan="2" | Less than or equal to 
| style="text-align:center;" | <code>a '''<=''' b</code> || {{yes}}
| {{cpp|1=bool K::operator <=(S const& b) const;}}
| {{cpp|1=bool operator <=(K const& a, S const& b);}}
|-
| {{rh}} colspan="2" | [[Three-way comparison]]<ref name="threewaycomparison" group="lower-alpha"/>{{efn|Possible return types: <code>std::weak_ordering</code>, <code>std::strong_ordering</code> and <code>std::partial_ordering</code> to which they all are convertible to.}}
| style="text-align:center;" | <code>a '''&lt;=&gt;''' b</code> || {{no}}
| {{cpp|1=auto K::operator <=>(const S &b);}}
| {{cpp|1=auto operator <=>(const K &a, const S &b);}}
|}