Constrained algorithms (since C++20)
From cppreference.com
C++20 provides constrained versions of most algorithms in the namespace std::ranges. In these algorithms, a range can be specified as either an iterator-sentinel pair or as a single range argument, and projections and pointer-to-member callables are supported. Additionally, the return types
Algorithm function objects
An algorithm function object (AFO), informally known as niebloid, is a customization point object
For an algorithm function object o, let S be the corresponding set of function templates. Then for any sequence of arguments args..., o(args...) is expression-equivalent to s(args...), where the result of name lookup for s is the overload set S
The constrained algorithms in the namespace std::ranges are defined as algorithm function objects. As a result:
- Explicit template argument lists cannot be specified when calling any of them.
- None of them are visible to argument-dependent lookup.
- When any of them are found by normal unqualified lookup as the name to the left of the function-call operator, argument-dependent lookup
Constrained algorithms
Defined in header
<algorithm> | |
Defined in namespace
std::ranges | |
Non-modifying sequence operations | |
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(C++20)(C++20)(C++20)
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checks if a predicate is true for all, any or none of the elements in a range (algorithm function object) |
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(C++20)
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applies a function to a range of elements (algorithm function object) |
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(C++20)
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applies a function object to the first N elements of a sequence (algorithm function object) |
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(C++20)(C++20)
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returns the number of elements satisfying specific criteria (algorithm function object) |
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(C++20)
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finds the first position where two ranges differ (algorithm function object) |
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(C++20)
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determines if two sets of elements are the same (algorithm function object) |
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(C++20)
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returns true if one range is lexicographically less than another (algorithm function object) |
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(C++20)(C++20)(C++20)
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finds the first element satisfying specific criteria (algorithm function object) |
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(C++23)(C++23)(C++23)
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finds the last element satisfying specific criteria (algorithm function object) |
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(C++20)
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finds the last sequence of elements in a certain range (algorithm function object) |
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(C++20)
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searches for any one of a set of elements (algorithm function object) |
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(C++20)
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finds the first two adjacent items that are equal (or satisfy a given predicate) (algorithm function object) |
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(C++20)
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searches for the first occurrence of a range of elements (algorithm function object) |
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(C++20)
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searches for the first occurrence of a number consecutive copies of an element in a range (algorithm function object) |
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(C++23)(C++23)
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checks if the range contains the given element or subrange (algorithm function object) |
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(C++23)
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checks whether a range starts with another range (algorithm function object) |
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(C++23)
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checks whether a range ends with another range (algorithm function object) |
Modifying sequence operations | |
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(C++20)(C++20)
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copies a range of elements to a new location (algorithm function object) |
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(C++20)
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copies a number of elements to a new location (algorithm function object) |
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(C++20)
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copies a range of elements in backwards order (algorithm function object) |
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(C++20)
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moves a range of elements to a new location (algorithm function object) |
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(C++20)
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moves a range of elements to a new location in backwards order (algorithm function object) |
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(C++20)
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assigns a range of elements a certain value (algorithm function object) |
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(C++20)
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assigns a value to a number of elements (algorithm function object) |
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(C++20)
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applies a function to a range of elements (algorithm function object) |
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(C++20)
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saves the result of a function in a range (algorithm function object) |
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(C++20)
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saves the result of N applications of a function (algorithm function object) |
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(C++20)(C++20)
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removes elements satisfying specific criteria (algorithm function object) |
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(C++20)(C++20)
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copies a range of elements omitting those that satisfy specific criteria (algorithm function object) |
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(C++20)(C++20)
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replaces all values satisfying specific criteria with another value (algorithm function object) |
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(C++20)(C++20)
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copies a range, replacing elements satisfying specific criteria with another value (algorithm function object) |
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(C++20)
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swaps two ranges of elements (algorithm function object) |
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(C++20)
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reverses the order of elements in a range (algorithm function object) |
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(C++20)
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creates a copy of a range that is reversed (algorithm function object) |
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(C++20)
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rotates the order of elements in a range (algorithm function object) |
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(C++20)
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copies and rotate a range of elements (algorithm function object) |
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(C++20)
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randomly re-orders elements in a range (algorithm function object) |
| shifts elements in a range (algorithm function object) |
|
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(C++20)
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selects N random elements from a sequence (algorithm function object) |
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(C++20)
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removes consecutive duplicate elements in a range (algorithm function object) |
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(C++20)
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creates a copy of some range of elements that contains no consecutive duplicates (algorithm function object) |
Partitioning operations | |
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(C++20)
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determines if the range is partitioned by the given predicate (algorithm function object) |
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(C++20)
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divides a range of elements into two groups (algorithm function object) |
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(C++20)
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copies a range dividing the elements into two groups (algorithm function object) |
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(C++20)
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divides elements into two groups while preserving their relative order (algorithm function object) |
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(C++20)
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locates the partition point of a partitioned range (algorithm function object) |
Sorting operations | |
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(C++20)
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checks whether a range is sorted into ascending order (algorithm function object) |
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(C++20)
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finds the largest sorted subrange (algorithm function object) |
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(C++20)
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sorts a range into ascending order (algorithm function object) |
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(C++20)
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sorts the first N elements of a range (algorithm function object) |
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(C++20)
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copies and partially sorts a range of elements (algorithm function object) |
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(C++20)
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sorts a range of elements while preserving order between equal elements (algorithm function object) |
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(C++20)
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partially sorts the given range making sure that it is partitioned by the given element (algorithm function object) |
Binary search operations (on sorted ranges) | |
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(C++20)
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returns an iterator to the first element not less than the given value (algorithm function object) |
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(C++20)
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returns an iterator to the first element greater than a certain value (algorithm function object) |
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(C++20)
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determines if an element exists in a partially-ordered range (algorithm function object) |
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(C++20)
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returns range of elements matching a specific key (algorithm function object) |
Set operations (on sorted ranges) | |
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(C++20)
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merges two sorted ranges (algorithm function object) |
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(C++20)
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merges two ordered ranges in-place (algorithm function object) |
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(C++20)
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returns true if one sequence is a subsequence of another (algorithm function object) |
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(C++20)
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computes the difference between two sets (algorithm function object) |
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(C++20)
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computes the intersection of two sets (algorithm function object) |
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(C++20)
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computes the symmetric difference between two sets (algorithm function object) |
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(C++20)
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computes the union of two sets (algorithm function object) |
Heap operations | |
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(C++20)
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checks if the given range is a max heap (algorithm function object) |
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(C++20)
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finds the largest subrange that is a max heap (algorithm function object) |
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(C++20)
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creates a max heap out of a range of elements (algorithm function object) |
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(C++20)
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adds an element to a max heap (algorithm function object) |
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(C++20)
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removes the largest element from a max heap (algorithm function object) |
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(C++20)
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turns a max heap into a range of elements sorted in ascending order (algorithm function object) |
Minimum/maximum operations | |
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(C++20)
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returns the greater of the given values (algorithm function object) |
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(C++20)
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returns the largest element in a range (algorithm function object) |
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(C++20)
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returns the smaller of the given values (algorithm function object) |
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(C++20)
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returns the smallest element in a range (algorithm function object) |
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(C++20)
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returns the smaller and larger of two elements (algorithm function object) |
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(C++20)
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returns the smallest and the largest elements in a range (algorithm function object) |
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(C++20)
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clamps a value between a pair of boundary values (algorithm function object) |
Permutation operations | |
|
(C++20)
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determines if a sequence is a permutation of another sequence (algorithm function object) |
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(C++20)
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generates the next greater lexicographic permutation of a range of elements (algorithm function object) |
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(C++20)
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generates the next smaller lexicographic permutation of a range of elements (algorithm function object) |
Constrained numeric operations
Defined in header
<numeric> | |
Defined in namespace
std::ranges | |
|
(C++23)
|
fills a range with successive increments of the starting value (algorithm function object) |
Constrained fold operations
Defined in header
<algorithm> | |
Defined in namespace
std::ranges | |
|
(C++23)
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left-folds a range of elements (algorithm function object) |
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(C++23)
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left-folds a range of elements using the first element as an initial value (algorithm function object) |
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(C++23)
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right-folds a range of elements (algorithm function object) |
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(C++23)
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right-folds a range of elements using the last element as an initial value (algorithm function object) |
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(C++23)
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left-folds a range of elements, and returns a pair (iterator, value) (algorithm function object) |
| left-folds a range of elements using the first element as an initial value, and returns a pair (iterator, optional) (algorithm function object) |
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Constrained uninitialized memory algorithms
Defined in header
<memory> | |
Defined in namespace
std::ranges | |
|
(C++20)
|
copies a range of objects to an uninitialized area of memory (algorithm function object) |
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(C++20)
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copies a number of objects to an uninitialized area of memory (algorithm function object) |
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(C++20)
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copies an object to an uninitialized area of memory, defined by a range (algorithm function object) |
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(C++20)
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copies an object to an uninitialized area of memory, defined by a start and a count (algorithm function object) |
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(C++20)
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moves a range of objects to an uninitialized area of memory (algorithm function object) |
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(C++20)
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moves a number of objects to an uninitialized area of memory (algorithm function object) |
| constructs objects by default-initialization in an uninitialized area of memory, defined by a range (algorithm function object) |
|
| constructs objects by default-initialization in an uninitialized area of memory, defined by a start and count (algorithm function object) |
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| constructs objects by value-initialization in an uninitialized area of memory, defined by a range (algorithm function object) |
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| constructs objects by value-initialization in an uninitialized area of memory, defined by a start and a count (algorithm function object) |
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(C++20)
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destroys a range of objects (algorithm function object) |
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(C++20)
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destroys a number of objects in a range (algorithm function object) |
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(C++20)
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destroys an object at a given address (algorithm function object) |
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(C++20)
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creates an object at a given address (algorithm function object) |
Constrained random number algorithms
Defined in header
<random> | |
Defined in namespace
std::ranges | |
|
(C++26)
|
fills a range with random numbers from a uniform random bit generator (algorithm function object) |
Return types
Defined in header
<algorithm> | |
Defined in namespace
std::ranges | |
|
(C++20)
|
provides a way to store an iterator and a function object as a single unit (class template) |
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(C++20)
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provides a way to store two iterators as a single unit (class template) |
|
(C++20)
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provides a way to store two iterators as a single unit (class template) |
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(C++20)
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provides a way to store three iterators as a single unit (class template) |
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(C++20)
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provides a way to store three iterators as a single unit (class template) |
|
(C++20)
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provides a way to store two objects or references of the same type as a single unit (class template) |
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(C++20)
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provides a way to store an iterator and a boolean flag as a single unit (class template) |
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(C++23)
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provides a way to store an iterator and a value as a single unit (class template) |
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(C++23)
|
provides a way to store an iterator and a value as a single unit (class template) |
Notes
| Feature-test macro | Value | Std | Feature |
|---|---|---|---|
__cpp_lib_algorithm_default_value_type |
202403L |
(C++26) | List-initialization for algorithms |
__cpp_lib_ranges |
201911L |
(C++20) | Ranges library and constrained algorithms |
__cpp_lib_ranges_contains |
202207L |
(C++23) | std::ranges::contains |
__cpp_lib_ranges_find_last |
202207L |
(C++23) | std::ranges::find_last |
__cpp_lib_ranges_fold |
202207L |
(C++23) | std::ranges fold algorithms
|
__cpp_lib_ranges_iota |
202202L |
(C++23) | std::ranges::iota |
__cpp_lib_ranges_starts_ends_with |
202106L |
(C++23) | std::ranges::starts_with, std::ranges::ends_with |
__cpp_lib_shift |
201806L |
(C++20) | std::shift_left, std::shift_right |
202202L |
(C++23) | std::ranges::shift_left, std::ranges::shift_right | |
__cpp_lib_ranges_generate_random |
202403L |
(C++26) | std::ranges::generate_random |
Defect reports
The following behavior-changing defect reports were applied retroactively to previously published C++ standards.
| DR | Applied to | Behavior as published | Correct behavior |
|---|---|---|---|
| P3136R1 | C++20 | niebloids were allowed to be specified as special entities other than function objects |
required to be specified as function objects |