std::clamp

 

C++

Language

Standard library headers

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

Technical Specifications

 

Algorithm library

Functions
Non-modifying sequence operations
all_ofany_ofnone_of (C++11)(C++11)(C++11) for_each countcount_if mismatch equal	findfind_iffind_if_not (C++11) find_end find_first_of adjacent_find search search_n
Modifying sequence operations
copycopy_if (C++11) copy_n (C++11) copy_backward move (C++11) move_backward (C++11) fill fill_n transform generate generate_n removeremove_if remove_copyremove_copy_if	replacereplace_if replace_copyreplace_copy_if swap swap_ranges iter_swap reverse reverse_copy rotate rotate_copy random_shuffleshuffle (until C++17)(C++11) sample (C++17) unique unique_copy
Partitioning operations
is_partitioned (C++11) partition partition_copy (C++11)	stable_partition partition_point (C++11)
Sorting operations (on sorted ranges)
is_sorted (C++11) is_sorted_until (C++11) sort	partial_sort partial_sort_copy stable_sort nth_element
Binary search operations (on sorted ranges)
lower_bound upper_bound	binary_search equal_range
Set operations (on sorted ranges)
merge inplace_merge includes	set_difference set_intersection set_symmetric_difference set_union
Heap operations
is_heap (C++11) is_heap_until (C++11) make_heap	push_heap pop_heap sort_heap
Minimum/maximum operations
max max_element min min_element minmax (C++11) minmax_element (C++11)	clamp lexicographical_compare is_permutation (C++11) next_permutation prev_permutation
Numeric operations
iota (C++11) accumulate inner_product	adjacent_difference partial_sum
C library
qsort	bsearch

 

Defined in header <algorithm>
template<class T> constexpr const T& clamp( const T& v, const T& lo, const T& hi );	(1)	(since C++17)
template<class T, class Compare> constexpr const T& clamp( const T& v, const T& lo, const T& hi, Compare comp );	(2)	(since C++17)

1) If v compares less than hi, returns the larger of v and lo, otherwise returns the smaller of v and hi. Uses operator< to compare the values.

2) Same as (1), but uses comp to compare the values.

Parameters

v	-	the value to clamp
lo,hi	-	the boundaries to clamp v to
comp	-	comparison function object (i.e. an object that satisfies the requirements of Compare) which returns ​true if lo is less than v and v is less than hi. The signature of the comparison function should be equivalent to the following:  bool cmp(const Type1 &a, const Type2 &b); The signature does not need to have const &, but the function object must not modify the objects passed to it. 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).

Return value

Reference to v if it is between the bounds, lo if v is smaller than lo, and hi if v is larger than hi.

If v compares equivalent to either bound, returns v.

Complexity

1) At most two comparisons

Possible implementation

First version
template<class T> constexpr const T& clamp( const T& v, const T& lo, const T& hi ) { return clamp( v, lo, hi, std::less<T>() ); }
Second version
template<class T, class Compare> constexpr const T& clamp( const T& val, const T& lo, const T& hi, Compare comp ) { return assert( !comp(hi, lo) ), comp(val, lo) ? lo : comp(hi, val) ? hi : val; }

Notes

Capturing the result of std::clamp by reference if one of the parameters is rvalue produces a dangling reference if that parameter is returned:

int n = -1;
const int& r = std::clamp(n, 0, 255);
// r is dangling

See also

min	returns the smaller of the given values (function template)
max	returns the greater of the given values (function template)