template< class T >
const T& max( const T& a, const T& b );
template< class T, class Compare >
const T& max( const T& a, const T& b, Compare comp );
Returns the greater of the given values.
1,2) Returns the greater of a and b.
1) Uses operator< to compare the values.
2) Use the comparison function comp to compare the values.
3,4) Returns the greatest of the values in initializer list ilist.
3) Uses operator< to compare the values.
4) Use the comparison function comp to compare the values.
[edit] Parameters a, b - the values to compare ilist - initializer list with the values to compare comp - comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if a is less than b.The signature of the comparison function should be equivalent to the following:
bool cmp(const Type1& a, const Type2& b);
While the signature does not need to have const&, the function must not modify the objects passed to it and must be able to accept all values of type (possibly const) Type1 and Type2 regardless of value category (thus, Type1& is not allowed, nor is Type1 unless for Type1 a move is equivalent to a copy(since C++11)).
The types Type1 and Type2 must be such that an object of type T can be implicitly converted to both of them.
1,2) The greater of a and b. If they are equivalent, returns a.
3,4) The greatest value in ilist. If several values are equivalent to the greatest, returns the leftmost one.
[edit] Complexity1) Exactly one comparison using operator<.
2) Exactly one application of the comparison function comp.
3,4) Given \(\scriptsize N\)N as ilist.size():
3) Exactly \(\scriptsize N-1\)N-1 comparisons using operator<.
4) Exactly \(\scriptsize N-1\)N-1 applications of the comparison function comp.
[edit] Possible implementation max (1)template<class T>
const T& max(const T& a, const T& b)
{
return (a < b) ? b : a;
}max (2)
template<class T, class Compare>
const T& max(const T& a, const T& b, Compare comp)
{
return (comp(a, b)) ? b : a;
}max (3)
template<class T>
T max(std::initializer_list<T> ilist)
{
return *std::max_element(ilist.begin(), ilist.end());
}max (4)
template<class T, class Compare>
T max(std::initializer_list<T> ilist, Compare comp)
{
return *std::max_element(ilist.begin(), ilist.end(), comp);
}[edit] Notes
Capturing the result of std::max by reference produces a dangling reference if one of the parameters is a temporary and that parameter is returned:
int n = -1; const int& r = std::max(n + 2, n * 2); // r is dangling[edit] Example
#include <algorithm>
#include <iomanip>
#include <iostream>
#include <string_view>
int main()
{
auto longest = [](const std::string_view s1, const std::string_view s2)
{
return s1.size() < s2.size();
};
std::cout << "Larger of 69 and 96 is " << std::max(69, 96) << "\n"
"Larger of 'q' and 'p' is '" << std::max('q', 'p') << "'\n"
"Largest of 010, 10, 0X10, and 0B10 is "
<< std::max({010, 10, 0X10, 0B10}) << '\n'
<< R"(Longest of "long", "short", and "int" is )"
<< std::quoted(std::max({"long", "short", "int"}, longest)) << '\n';
}
Output:
Larger of 69 and 96 is 96 Larger of 'q' and 'p' is 'q' Largest of 010, 10, 0X10, and 0B10 is 16 Longest of "long", "short", and "int" is "short"[edit] Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
DR Applied to Behavior as published Correct behavior LWG 281 C++98T was required to be CopyConstructible for overloads (1,2) not required LWG 2239 C++98
T was required to be LessThanComparable for
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