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std::ranges:: replace, std::ranges:: replace_if

From cppreference.net
C++
Algorithm library
Constrained algorithms and algorithms on ranges (C++20)
Constrained algorithms, e.g. ranges::copy , ranges::sort , ...
Execution policies (C++17)
Non-modifying sequence operations
Batch operations
(C++17)
Search operations
Modifying sequence operations
Copy operations
(C++11)
(C++11)
(C++11)
Swap operations
Transformation operations
Generation operations
Removing operations
Order-changing operations
(until C++17) (C++11)
(C++20) (C++20)
Sampling operations
(C++17)

Sorting and related operations
Partitioning operations
Sorting operations
Binary search operations
(on partitioned ranges)
Set operations (on sorted ranges)
Merge operations (on sorted ranges)
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(C++20)
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C library
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Constrained algorithms
All names in this menu belong to namespace std::ranges
Non-modifying sequence operations
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
Operations on uninitialized storage
Return types
Definido en el encabezado <algorithm>
Firma de llamada
(1)
template < std:: input_iterator I, std:: sentinel_for < I > S,

class T1, class T2, class Proj = std:: identity >
requires std:: indirectly_writable < I, const T2 & > &&
std:: indirect_binary_predicate
< ranges:: equal_to , std :: projected < I, Proj > , const T1 * >
constexpr I replace ( I first, S last, const T1 & old_value,

const T2 & new_value, Proj proj = { } ) ;
(desde C++20)
(hasta C++26)
template < std:: input_iterator I, std:: sentinel_for < I > S,

class Proj = std:: identity ,
class T1 = std :: projected_value_t < I, Proj > , class T2 = T1 >
requires std:: indirectly_writable < I, const T2 & > &&
std:: indirect_binary_predicate
< ranges:: equal_to , std :: projected < I, Proj > , const T1 * >
constexpr I replace ( I first, S last, const T1 & old_value,

const T2 & new_value, Proj proj = { } ) ;
(desde C++26)
(2)
template < ranges:: input_range R,

class T1, class T2, class Proj = std:: identity >
requires std:: indirectly_writable < ranges:: iterator_t < R > , const T2 & > &&
std:: indirect_binary_predicate
< ranges:: equal_to ,
std :: projected < ranges:: iterator_t < R > , Proj > , const T1 * >
constexpr ranges:: borrowed_iterator_t < R >
replace ( R && r, const T1 & old_value,

const T2 & new_value, Proj proj = { } ) ;
(desde C++20)
(hasta C++26)
template < ranges:: input_range R,

class Proj = std:: identity ,
class T1 = std :: projected_value_t < ranges:: iterator_t < R > , Proj > ,
class T2 = T1 >
requires std:: indirectly_writable < ranges:: iterator_t < R > , const T2 & > &&
std:: indirect_binary_predicate
< ranges:: equal_to ,
std :: projected < ranges:: iterator_t < R > , Proj > , const T1 * >
constexpr ranges:: borrowed_iterator_t < R >
replace ( R && r, const T1 & old_value,

const T2 & new_value, Proj proj = { } ) ;
(desde C++26)
(3)
template < std:: input_iterator I, std:: sentinel_for < I > S,

class T, class Proj = std:: identity ,
std:: indirect_unary_predicate < std :: projected < I, Proj >> Pred >
requires std:: indirectly_writable < I, const T & >
constexpr I replace_if ( I first, S last, Pred pred,

const T & new_value, Proj proj = { } ) ;
(desde C++20)
(hasta C++26)
template < std:: input_iterator I, std:: sentinel_for < I > S,

class Proj = std:: identity ,
class T = std :: projected_value_t < I, Proj > ,
std:: indirect_unary_predicate < std :: projected < I, Proj >> Pred >
requires std:: indirectly_writable < I, const T & >
constexpr I replace_if ( I first, S last, Pred pred,

const T & new_value, Proj proj = { } ) ;
(desde C++26)
(4)
template < ranges:: input_range R, class T, class Proj = std:: identity ,

std:: indirect_unary_predicate <
std :: projected < ranges:: iterator_t < R > , Proj >> Pred >
requires std:: indirectly_writable < ranges:: iterator_t < R > , const T & >
constexpr ranges:: borrowed_iterator_t < R >

replace_if ( R && r, Pred pred, const T & new_value, Proj proj = { } ) ;
(desde C++20)
(hasta C++26)
template < ranges:: input_range R, class Proj = std:: identity ,

class T = std :: projected_value_t < ranges:: iterator_t < R > , Proj > ,
std:: indirect_unary_predicate <
std :: projected < ranges:: iterator_t < R > , Proj >> Pred >
requires std:: indirectly_writable < ranges:: iterator_t < R > , const T & >
constexpr ranges:: borrowed_iterator_t < R >

replace_if ( R && r, Pred pred, const T & new_value, Proj proj = { } ) ;
(desde C++26)

Reemplaza todos los elementos que satisfacen criterios específicos con new_value en el rango [ first , last ) .

1) Reemplaza todos los elementos que son iguales a old_value , usando std:: invoke ( proj, * i ) == old_value para comparar.
3) Reemplaza todos los elementos para los cuales el predicado pred evalúa a true , donde la expresión evaluada es std:: invoke ( pred, std:: invoke ( proj, * i ) ) .
2,4) Igual que (1,3) , pero utiliza r como el rango, como si usara ranges:: begin ( r ) como first y ranges:: end ( r ) como last .

Las entidades similares a funciones descritas en esta página son algorithm function objects (conocidas informalmente como niebloids ), es decir:

Contenidos

Parámetros

first, last - el par iterador-centinela que define el rango de elementos a procesar
r - el rango de elementos a procesar
old_value - el valor de los elementos a reemplazar
new_value - el valor a utilizar como reemplazo
pred - predicado a aplicar a los elementos proyectados
proj - proyección a aplicar a los elementos

Valor de retorno

Un iterador igual a last .

Complejidad

Exactamente ranges:: distance ( first, last ) aplicaciones del predicado correspondiente comp y cualquier proyección proj .

Notas

Debido a que el algoritmo toma old_value y new_value por referencia, puede tener un comportamiento inesperado si cualquiera de ellos es una referencia a un elemento del rango [ first , last ) .

Macro de prueba de características Valor Estándar Característica
__cpp_lib_algorithm_default_value_type 202403 (C++26) Inicialización de lista para algoritmos ( 1-4 )

Implementación posible

reemplazar (1,2) 
struct replace_fn
{
    template<std::input_iterator I, std::sentinel_for<I> S, class Proj = std::identity,
             class T1 = std::projected_value_t<I, Proj>, class T2 = T1>
    requires std::indirectly_writable<I, const T2&> && 
             std::indirect_binary_predicate
                 <ranges::equal_to, std::projected<I, Proj>, const T1*>
    constexpr I operator()(I first, S last, const T1& old_value,
                           const T2& new_value, Proj proj = {}) const
    {
        for (; first != last; ++first)
            if (old_value == std::invoke(proj, *first))
                *first = new_value;
        return first;
    }
    template<ranges::input_range R, class Proj = std::identity
             class T1 = std::projected_value_t<ranges::iterator_t<R>, Proj>,
             class T2 = T1>
    requires std::indirectly_writable<ranges::iterator_t<R>, const T2&> &&
             std::indirect_binary_predicate<ranges::equal_to,
             std::projected<ranges::iterator_t<R>, Proj>, const T1*>
    constexpr ranges::borrowed_iterator_t<R>
        operator()(R&& r, const T1& old_value,
                   const T2& new_value, Proj proj = {}) const
    {
        return (*this)(ranges::begin(r), ranges::end(r), old_value,
                       new_value, std::move(proj));
    }
};
inline constexpr replace_fn replace{};
replace_if (3,4) 
struct replace_if_fn
{
    template<std::input_iterator I, std::sentinel_for<I> S,
             class Proj = std::identity, class T = std::projected_value_t<I, Proj>,
             std::indirect_unary_predicate<std::projected<I, Proj>> Pred>
    requires std::indirectly_writable<I, const T&>
    constexpr I operator()(I first, S last, Pred pred,
                           const T& new_value, Proj proj = {}) const
    {
        for (; first != last; ++first)
            if (!!std::invoke(pred, std::invoke(proj, *first)))
                *first = new_value;
        return std::move(first);
    }
    template<ranges::input_range R, class Proj = std::identity,
             class T = std::projected_value_t<ranges::iterator_t<R>, Proj>
             std::indirect_unary_predicate
                 <std::projected<ranges::iterator_t<R>, Proj>> Pred>
    requires std::indirectly_writable<ranges::iterator_t<R>, const T&>
    constexpr ranges::borrowed_iterator_t<R>
        operator()(R&& r, Pred pred, const T& new_value, Proj proj = {}) const
    {
        return (*this)(ranges::begin(r), ranges::end(r), std::move(pred),
                       new_value, std::move(proj));
    }
};
inline constexpr replace_if_fn replace_if{};

Ejemplo

Ejecutar este código 
#include <algorithm>
#include <array>
#include <complex>
#include <iostream>
void println(const auto& v)
{
    for (const auto& e : v)
        std::cout << e << ' ';
    std::cout << '\n';
}
int main()
{
    namespace ranges = std::ranges;
    std::array p{1, 6, 1, 6, 1, 6};
    println(p);
    ranges::replace(p, 6, 9);
    println(p);
    std::array q{1, 2, 3, 6, 7, 8, 4, 5};
    println(q);
    ranges::replace_if(q, [](int x) { return 5 < x; }, 5);
    println(q);
    std::array<std::complex<double>, 2> nums{{{1, 3}, {1, 3}}};
    println(nums);
    #ifdef __cpp_lib_algorithm_default_value_type
        ranges::replace(nums, {1, 3}, {4, 2});
    #else
        ranges::replace(nums, std::complex<double>{1, 3}, std::complex<double>{4, 2});
    #endif
    println(nums);
}

Salida: 

1 6 1 6 1 6
1 9 1 9 1 9
1 2 3 6 7 8 4 5
1 2 3 5 5 5 4 5
(1,3) (1,3)
(4,2) (4,2)

Véase también

(C++20) (C++20)
copia un rango, reemplazando elementos que cumplen criterios específicos con otro valor
(objeto función de algoritmo)
reemplaza todos los valores que cumplen criterios específicos con otro valor
(plantilla de función)