# std::min

From cppreference.com
< cpp‎ | algorithm

Defined in header `<algorithm>` |  |
| (1) |
template< class T > const T& min( const T& a, const T& b ); |  | (until C++14)
template< class T > constexpr const T& min( const T& a, const T& b ); |  | (since C++14)
| (2) |
template< class T, class Compare > const T& min( const T& a, const T& b, Compare comp ); |  | (until C++14)
template< class T, class Compare > constexpr const T& min( const T& a, const T& b, Compare comp ); |  | (since C++14)
| (3) |
template< class T > T min( std::initializer_list<T> ilist ); |  | (since C++11) (until C++14)
template< class T > constexpr T min( std::initializer_list<T> ilist ); |  | (since C++14)
| (4) |
template< class T, class Compare > T min( std::initializer_list<T> ilist, Compare comp ); |  | (since C++11) (until C++14)
template< class T, class Compare > constexpr T min( std::initializer_list<T> ilist, Compare comp ); |  | (since C++14)

Returns the smaller of the given values.

1-2) Returns the smaller of a and b.
3-4) Returns the smallest of the values in initializer list ilist.

Overloads (1,3) use `operator<` to compare the values, overloads (2,4) 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 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 in order to use overloads (1,3).
- `T` must meet the requirements of CopyConstructible in order to use overloads (3,4).

### Return value

1-2) The smaller of a and b. If the values are equivalent, returns a.
3-4) The smallest value in ilist. If several values are equivalent to the smallest, returns the leftmost such value.

### Complexity

1-2) Exactly one comparison
3-4) Exactly ilist.size() - 1 comparisons

### Possible implementation

min (1)
    template<class T>
    const T& min(const T& a, const T& b)
    {
        return (b < a) ? b : a;
    }
min (2)
    template<class T, class Compare>
    const T& min(const T& a, const T& b, Compare comp)
    {
        return (comp(b, a)) ? b : a;
    }
min (3)
    template<class T>
    T min(std::initializer_list<T> ilist)
    {
        return *std::min_element(ilist.begin(), ilist.end());
    }
min (4)
    template<class T, class Compare>
    T min(std::initializer_list<T> ilist, Compare comp)
    {
        return *std::min_element(ilist.begin(), ilist.end(), comp);
    }

### Notes

Capturing the result of `std::min` 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::min(n - 1, n + 1); // r is dangling

### Example

Run this code

    #include <algorithm>
    #include <iostream>
    #include <string_view>

    int main()
    {
        std::cout << "smaller of 1 and 9999 is " << std::min(1, 9999) << '\n'
                  << "smaller of 'a', and 'b' is '" << std::min('a', 'b') << "'\n"
                  << "shortest of \"foo\", \"bar\", and \"hello\" is \""
                  << std::min({"foo", "bar", "hello"},
                              [](const std::string_view s1, const std::string_view s2)
                              {
                                  return s1.size() < s2.size();
                              }) << "\"\n";
    }

Output:

    smaller of 1 and 9999 is 1
    smaller of 'a', and 'b' is 'a'
    shortest of "foo", "bar", and "hello" is "foo"

### 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++98 | `T` was required to be CopyConstructible for overloads (1,2) | not required

### See also

max | returns the greater of the given values (function template)
minmax (C++11) | returns the smaller and larger of two elements (function template)
min_element | returns the smallest element in a range (function template)
clamp (C++17) | clamps a value between a pair of boundary values (function template)
ranges::min (C++20) | returns the smaller of the given values (niebloid)

Retrieved from "https://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/min&oldid=149914"