Constrained algorithms and algorithms on ranges(C++20) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Constrained algorithms, e.g.ranges::copy,ranges::sort, ... | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Execution policies(C++17) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Numeric operations | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Operations on uninitialized memory | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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std::ranges
Non-modifying sequence operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Modifying sequence operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Partitioning operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sorting operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Binary search operations (on sorted ranges) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Set operations (on sorted ranges) | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Heap operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Minimum/maximum operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Permutation operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Fold operations | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Operations on uninitialized storage | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Return types | ||||||||||||||||||||||||||||||||||||||||||||||||||||||
Defined in header <algorithm> | ||
Call signature | ||
(1) | ||
template<std::input_iterator I,std::sentinel_for<I> S, class T,class Proj=std::identity> | (since C++20) (until C++26) | |
template<std::input_iterator I,std::sentinel_for<I> S, class Proj=std::identity, | (since C++26) | |
(2) | ||
template<ranges::input_range R,class T,class Proj=std::identity> requiresstd::indirect_binary_predicate | (since C++20) (until C++26) | |
template<ranges::input_range R,class Proj=std::identity, class T= std::projected_value_t<ranges::iterator_t<R>, Proj>> | (since C++26) | |
template<std::input_iterator I,std::sentinel_for<I> S, class Proj=std::identity, | (3) | (since C++20) |
template<ranges::input_range R,class Proj=std::identity, std::indirect_unary_predicate | (4) | (since C++20) |
template<std::input_iterator I,std::sentinel_for<I> S, class Proj=std::identity, | (5) | (since C++20) |
template<ranges::input_range R,class Proj=std::identity, std::indirect_unary_predicate | (6) | (since C++20) |
Returns the first element in the range[
first,
last)
that satisfies specific criteria:
find
searches for an element equal tovalue.find_if
searches for an element for which predicatepred returnstrue.find_if_not
searches for an element for which predicatepred returnsfalse.The function-like entities described on this page arealgorithm function objects (informally known asniebloids), that is:
Contents |
first, last | - | the iterator-sentinel pair defining therange of elements to examine |
r | - | the range of the elements to examine |
value | - | value to compare the elements to |
pred | - | predicate to apply to the projected elements |
proj | - | projection to apply to the elements |
Iterator to the first element satisfying the condition or iterator equal tolast if no such element is found.
At mostlast- first applications of the predicate and projection.
find (1) |
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struct find_fn{template<std::input_iterator I,std::sentinel_for<I> S,class Proj=std::identity,class T= std::projected_value_t<I, Proj>> requiresstd::indirect_binary_predicate<ranges::equal_to, std::projected<I, Proj>,const T*>constexpr I operator()(I first, S last,const T& value, Proj proj={})const{for(; first!= last;++first)if(std::invoke(proj,*first)== value)return first;return first;} template<ranges::input_range R,class T,class Proj=std::identity> requiresstd::indirect_binary_predicate<ranges::equal_to, std::projected<ranges::iterator_t<R>, Proj>,const T*>constexprranges::borrowed_iterator_t<R> operator()(R&& r,const T& value, Proj proj={})const{return(*this)(ranges::begin(r),ranges::end(r), value,std::ref(proj));}}; inlineconstexpr find_fn find; |
find_if (3) |
struct find_if_fn{template<std::input_iterator I,std::sentinel_for<I> S,class Proj=std::identity,std::indirect_unary_predicate<std::projected<I, Proj>> Pred>constexpr I operator()(I first, S last, Pred pred, Proj proj={})const{for(; first!= last;++first)if(std::invoke(pred,std::invoke(proj,*first)))return first;return first;} template<ranges::input_range R,class Proj=std::identity,std::indirect_unary_predicate<std::projected<ranges::iterator_t<R>, Proj>> Pred>constexprranges::borrowed_iterator_t<R> operator()(R&& r, Pred pred, Proj proj={})const{return(*this)(ranges::begin(r),ranges::end(r),std::ref(pred),std::ref(proj));}}; inlineconstexpr find_if_fn find_if; |
find_if_not (5) |
struct find_if_not_fn{template<std::input_iterator I,std::sentinel_for<I> S,class Proj=std::identity,std::indirect_unary_predicate<std::projected<I, Proj>> Pred>constexpr I operator()(I first, S last, Pred pred, Proj proj={})const{for(; first!= last;++first)if(!std::invoke(pred,std::invoke(proj,*first)))return first;return first;} template<ranges::input_range R,class Proj=std::identity,std::indirect_unary_predicate<std::projected<ranges::iterator_t<R>, Proj>> Pred>constexprranges::borrowed_iterator_t<R> operator()(R&& r, Pred pred, Proj proj={})const{return(*this)(ranges::begin(r),ranges::end(r),std::ref(pred),std::ref(proj));}}; inlineconstexpr find_if_not_fn find_if_not; |
Feature-test macro | Value | Std | Feature |
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__cpp_lib_algorithm_default_value_type | 202403 | (C++26) | List-initialization for algorithms(1,2) |
#include <algorithm>#include <cassert>#include <complex>#include <format>#include <iostream>#include <iterator>#include <string>#include <vector> void projector_example(){struct folk_info{unsigned uid;std::string name, position;}; std::vector<folk_info> folks{{0,"Ana","dev"},{1,"Bob","devops"},{2,"Eve","ops"}}; constauto who{"Eve"};if(auto it= std::ranges::find(folks, who,&folk_info::name); it!= folks.end())std::cout<<std::format("Profile:\n"" UID: {}\n"" Name: {}\n"" Position: {}\n\n", it->uid, it->name, it->position);} int main(){namespace ranges= std::ranges; projector_example(); constint n1=3;constint n2=5;constauto v={4,1,3,2}; if(ranges::find(v, n1)!= v.end())std::cout<<"v contains: "<< n1<<'\n';elsestd::cout<<"v does not contain: "<< n1<<'\n'; if(ranges::find(v.begin(), v.end(), n2)!= v.end())std::cout<<"v contains: "<< n2<<'\n';elsestd::cout<<"v does not contain: "<< n2<<'\n'; auto is_even=[](int x){return x%2==0;}; if(auto result= ranges::find_if(v.begin(), v.end(), is_even); result!= v.end())std::cout<<"First even element in v: "<<*result<<'\n';elsestd::cout<<"No even elements in v\n"; if(auto result= ranges::find_if_not(v, is_even); result!= v.end())std::cout<<"First odd element in v: "<<*result<<'\n';elsestd::cout<<"No odd elements in v\n"; auto divides_13=[](int x){return x%13==0;}; if(auto result= ranges::find_if(v, divides_13); result!= v.end())std::cout<<"First element divisible by 13 in v: "<<*result<<'\n';elsestd::cout<<"No elements in v are divisible by 13\n"; if(auto result= ranges::find_if_not(v.begin(), v.end(), divides_13); result!= v.end())std::cout<<"First element indivisible by 13 in v: "<<*result<<'\n';elsestd::cout<<"All elements in v are divisible by 13\n"; std::vector<std::complex<double>> nums{{4,2}};#ifdef __cpp_lib_algorithm_default_value_type// T gets deduced in (2) making list-initialization possibleconstauto it= ranges::find(nums,{4,2});#elseconstauto it= ranges::find(nums,std::complex<double>{4,2});#endifassert(it== nums.begin());}
Output:
Profile: UID: 2 Name: Eve Position: ops v contains: 3v does not contain: 5First even element in v: 4First odd element in v: 1No elements in v are divisible by 13First element indivisible by 13 in v: 4
(C++20) | finds the first two adjacent items that are equal (or satisfy a given predicate) (algorithm function object)[edit] |
(C++20) | finds the last sequence of elements in a certain range (algorithm function object)[edit] |
(C++20) | searches for any one of a set of elements (algorithm function object)[edit] |
(C++20) | finds the first position where two ranges differ (algorithm function object)[edit] |
(C++20) | searches for the first occurrence of a range of elements (algorithm function object)[edit] |
(C++11) | finds the first element satisfying specific criteria (function template)[edit] |