std::experimental::ranges:: find, std::experimental::ranges:: find_if, std::experimental::ranges:: find_if_not

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C++
Experimental
Ranges
Algorithms library
Non-modifying sequence operations
find find_if find_if_not
Modifying sequence operations
Partitioning operations
Sorting operations
Binary search operations
Set operations (on sorted ranges)
Heap operations
Minimum/maximum operations
Permutations
template < InputIterator I, Sentinel < I > S, class T, class Proj = ranges:: identity >

requires IndirectRelation < ranges:: equal_to <> , projected < I, Proj > , const T * >

I find ( I first, S last, const T & value, Proj proj = Proj { } ) ;
(1) (ranges TS)
template < InputRange R, class T, class Proj = ranges:: identity >

requires IndirectRelation < ranges:: equal_to <> ,
projected < ranges:: iterator_t < R > , Proj > , const T * >

ranges:: safe_iterator_t < R > find ( R && r, const T & value, Proj proj = Proj { } ) ;
(2) (ranges TS)
template < InputIterator I, Sentinel < I > S, class Proj = ranges:: identity ,

IndirectUnaryPredicate < projected < I, Proj >> Pred >

I find_if ( I first, S last, Pred pred, Proj proj = Proj { } ) ;
(3) (ranges TS)
template < InputRange R, class Proj = ranges:: identity ,

IndirectUnaryPredicate < projected < ranges:: iterator_t < R > , Proj >> Pred >

ranges:: safe_iterator_t < R > find_if ( R && r, Pred pred, Proj proj = Proj { } ) ;
(4) (ranges TS)
template < InputIterator I, Sentinel < I > S, class Proj = ranges:: identity ,

IndirectUnaryPredicate < projected < I, Proj >> Pred >

I find_if_not ( I first, S last, Pred pred, Proj proj = Proj { } ) ;
(5) (ranges TS)
template < InputRange R, class Proj = ranges:: identity ,

IndirectUnaryPredicate < projected < ranges:: iterator_t < R > , Proj >> Pred >

ranges:: safe_iterator_t < R > find_if_not ( R && r, Pred pred, Proj proj = Proj { } ) ;
(6) (ranges TS)

Returns the first element in the range [ first , last ) that satisfies specific criteria:

1) find searches for an element whose projected value is equal to value (i.e., value == ranges:: invoke ( proj, * i ) ).
3) find_if searches for an element for whose projected value predicate p returns true (i.e., ranges:: invoke ( pred, ranges:: invoke ( proj, * i ) ) ) is true ).
5) find_if_not searches for an element for whose projected value predicate q returns false (i.e., ranges:: invoke ( pred, ranges:: invoke ( proj, * i ) ) ) is false ).
2,4,6) Same as (1,3,5) , but uses r as the source range, as if using ranges:: begin ( r ) as first and ranges:: end ( r ) as last .

Notwithstanding the declarations depicted above, the actual number and order of template parameters for algorithm declarations is unspecified. Thus, if explicit template arguments are used when calling an algorithm, the program is probably non-portable.

Parameters

first, last - the range of elements to examine
r - the range of elements to examine
value - value to compare the projected elements to
pred - predicate to apply to the projected elements
proj - projection to apply to the elements

Return value

Iterator to the first element satisfying the condition. If no such element is found, returns an iterator that compares equal to last .

Complexity

At most last - first applications of the predicate and projection.

Possible implementation

First version 
template<InputIterator I, Sentinel<I> S, class T, class Proj = ranges::identity>
    requires IndirectRelation<ranges::equal_to<>, projected<I, Proj>, const T*>
I find(I first, S last, const T& value, Proj proj = Proj{})
{
    for (; first != last; ++first)
        if (ranges::invoke(proj, *first) == value)
            break;
    return first;
}
Second version 
template<InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
         IndirectUnaryPredicate<projected<I, Proj>> Pred>
I find_if(I first, S last, Pred pred, Proj proj = Proj{})
{
    for (; first != last; ++first)
        if (ranges::invoke(pred, ranges::invoke(proj, *first)))
            break;
    return first;
}
Third version 
template<InputIterator I, Sentinel<I> S, class Proj = ranges::identity,
         IndirectUnaryPredicate<projected<I, Proj>> Pred>
I find_if_not(I first, S last, Pred pred, Proj proj = Proj{})
{
    for (; first != last; ++first)
        if (!ranges::invoke(pred, ranges::invoke(proj, *first)))
            break;
    return first;
}

Example

This section is incomplete
Reason: no example

See also

(C++11)
finds the first element satisfying specific criteria
(function template)
finds the first two adjacent items that are equal (or satisfy a given predicate)
(function template)
finds the last sequence of elements in a certain range
(function template)
searches for any one of a set of elements
(function template)
finds the first position where two ranges differ
(function template)
searches for a range of elements
(function template)
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