std::max

 

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Template:ddcl list begin <tr class="t-dsc-header">

<td>

Defined in header <algorithm>

</td>

<td></td> <td></td> </tr> <tr class="t-dcl ">

<td >

template< class T >
const T& max( const T& a, const T& b );

</td>

<td > (1) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

<td >

template< class T, class Compare >
const T& max( const T& a, const T& b, Compare comp );

</td>

<td > (2) </td> <td class="t-dcl-nopad"> </td> </tr> <tr class="t-dcl ">

<td >

template< class T >
T max( std::initializer_list<T> ilist);

</td>

<td > (3) </td> <td > (since C++11) </td> </tr> <tr class="t-dcl ">

<td >

template< class T, class Compare >
T max( std::initializer_list<T> ilist, Compare comp );

</td>

<td > (4) </td> <td > (since C++11) </td> </tr> Template:ddcl list end

1-2) Returns the greater of the two values.

3-4) Returns the greatest of the values in initializer list ilist.

The (1,3) versions use operator< to compare the values, the (2,4) versions use the given comparison function comp.

Parameters

a, b	-	the values to compare
ilist	-	initializer list with the values to compare
cmp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if 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.
Type requirements
- T must meet the requirements of LessThanComparable. for the overloads (1) and (3)
- T must meet the requirements of CopyConstructible. for the overloads (3) and (4)

Return value

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.

Complexity

1-2) Constant

3-4) Linear in ilist.size()

Possible implementation

First version
template<class T> const T& max(const T& a, const T& b) { return (a < b) ? b : a; }
Second version
template<class T, class Compare> const T& max(const T& a, const T& b, Compare comp) { return (comp(a, b)) ? b : a; }
Third version
template< class T > T max( std::initializer_list<T> ilist) { return *std::max_element(ilist.begin(), ilist.end()); }
Fourth version
template< class T, class Compare > T max( std::initializer_list<T> ilist, Compare comp ) { return *std::max_element(ilist.begin(), ilist.end(), comp); }

Example

Run this code

#include <algorithm>
#include <iostream>
#include <string> 
int main()
{
    std::cout << "larger of 1 and 9999: " << std::max(1, 9999) << '\n'
              << "larger of 'a', and 'b': " << std::max('a', 'b') << '\n'
              << "longest of \"foo\", \"bar\", and \"hello\": " <<
                  std::max( { "foo", "bar", "hello" },
                            [](const std::string& s1, const std::string& s2) {
                                 return s1.size() < s2.size();
                             }) << '\n';
}

Output:

larger of 1 and 9999: 9999
larger of 'a', and 'b': b
longest of "foo", "bar", and "hello": hello

See also

Template:cpp/algorithm/dcl list minTemplate:cpp/algorithm/dcl list minmaxTemplate:cpp/algorithm/dcl list max element