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std::clamp(3) C++ Standard Libary std::clamp(3) NAME std::clamp - std::clamp Synopsis Defined in header <algorithm> template<class T> (1) (since C++17) constexpr const T& clamp( const T& v, const T& lo, const T& hi ); template<class T, class Compare> constexpr const T& clamp( const T& v, const T& lo, const T& hi, (2) (since C++17) Compare comp ); 1) If v compares less than lo, returns lo; otherwise if hi compares less than v, returns hi; otherwise returns v. Uses operator< to compare the values. 2) Same as (1), but uses comp to compare the values. The behavior is undefined if the value of lo is greater than hi. Parameters v - the value to clamp lo,hi - the boundaries to clamp v to comparison function object (i.e. an object that satisfies the requirements of Compare) which returns true if the first argument is less than the second. The signature of the comparison function should be equiva- lent to the following: bool cmp(const Type1 &a, const Type2 &b); comp - While the signature does not need to have const &, the func- tion 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). However, if NaN is avoided, T can be a floating-point type. Return value Reference to lo if v is less than lo, reference to hi if hi is less than v, otherwise reference to v. Complexity 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, less{}); } Second version template<class T, class Compare> constexpr const T& clamp( const T& v, const T& lo, const T& hi, Com- pare comp ) { return comp(v, lo) ? lo : comp(hi, v) ? hi : v; } Notes Capturing the result of std::clamp 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::clamp(n, 0, 255); // r is dangling If v compares equivalent to either bound, returns a reference to v, not the bound. Feature-test macro: __cpp_lib_clamp Example // Run this code #include <cstdint> #include <algorithm> #include <iostream> #include <iomanip> int main() { std::cout << " raw clamped to int8_t clamped to uint8_t\n"; for(int const v: {-129, -128, -1, 0, 42, 127, 128, 255, 256}) { std::cout << std::setw(04) << v << std::setw(20) << std::clamp(v, INT8_MIN, INT8_MAX) << std::setw(21) << std::clamp(v, 0, UINT8_MAX) << '\n'; } } Output: raw clamped to int8_t clamped to uint8_t -129 -128 0 -128 -128 0 -1 -1 0 0 0 0 42 42 42 127 127 127 128 127 128 255 127 255 256 127 255 See also min returns the smaller of the given values (function template) max returns the greater of the given values (function template) in_range checks if an integer value is in the range of a given integer type (C++20) (function template) ranges::clamp clamps a value between a pair of boundary values (C++20) (niebloid) http://cppreference.com 2022.07.31 std::clamp(3)
NAME | Synopsis | Parameters | Type requirements | Return value | Complexity | Possible implementation | First version | Second version | Notes | Example | Output: | See also
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