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c++ auto

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ALeonidou answered on May 11, 2021 Popularity 10/10 Helpfulness 2/10

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c++ auto

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//When using auto variables, the data type is decided in initialisation

#include <iostream>
using namespace std;

int main() {
    auto IntegerVar=25;   //creates integer type variable
    auto FloatVar=26.77;  //creates float type variable
    auto StringVar="Hello";  //creates string type variable
    auto CharVar="C";   //creates char type variable
  
    cout<<"CREATING VARIABLES USING AUTO DATA TYPE\n\n";
    cout<<"Integer: "<<IntegerVar<<endl;
    cout<<"Float: "<<FloatVar<<endl;
    cout<<"String: "<<StringVar<<endl;
    cout<<"Char: "<<CharVar;
    
    cout<<"\n\n";
    return 0;
}

Popularity 10/10 Helpfulness 2/10 Language cpp

Source: Grepper

Tags: auto c++

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Contributed on May 11 2022

ALeonidou

0 Answers Avg Quality 2/10

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auto c++

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#include <iostream>
#include <vector>
 
int main()
{
    std::vector<int> v = {0, 1, 2, 3, 4, 5};
 
    for (const int& i : v) // access by const reference
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (auto i : v) // access by value, the type of i is int
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (auto&& i : v) // access by forwarding reference, the type of i is int&
        std::cout << i << ' ';
    std::cout << '\n';
 
    const auto& cv = v;
 
    for (auto&& i : cv) // access by f-d reference, the type of i is const int&
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (int n : {0, 1, 2, 3, 4, 5}) // the initializer may be a braced-init-list
        std::cout << n << ' ';
    std::cout << '\n';
 
    int a[] = {0, 1, 2, 3, 4, 5};
    for (int n : a) // the initializer may be an array
        std::cout << n << ' ';
    std::cout << '\n';
 
    for ([[maybe_unused]] int n : a)  
        std::cout << 1 << ' '; // the loop variable need not be used
    std::cout << '\n';
 
    for (auto n = v.size(); auto i : v) // the init-statement (C++20)
        std::cout << --n + i << ' ';
    std::cout << '\n';
 
    for (typedef decltype(v)::value_type elem_t; elem_t i : v)
    // typedef declaration as init-statement (C++20)
        std::cout << i << ' ';
    std::cout << '\n';
 
    for (using elem_t = decltype(v)::value_type; elem_t i : v)
    // alias declaration as init-statement (C++23)
        std::cout << i << ' ';
    std::cout << '\n';
}

Popularity 9/10 Helpfulness 3/10 Language cpp

Source: en.cppreference.com

Tags: auto

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Contributed on Apr 01 2024

Dmytro Skorobahat'ko

0 Answers Avg Quality 2/10

for auto c++

Comment

for (auto&& [first,second] : mymap) {
    // use first and second
}

Popularity 10/10 Helpfulness 2/10 Language cpp

Source: en.cppreference.com

Tags: auto

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Contributed on Oct 14 2021

Smiling Seal

0 Answers Avg Quality 2/10

auto& in c++

Comment

    Use auto && for the ability to modify and discard values of the sequence within the loop. (That is, unless the container provides a read-only view, such as std::initializer_list, in which case it will be effectively an auto const &.)
    Use auto & to modify the values of the sequence in a meaningful way.
    Use auto const & for read-only access.
    Use auto to work with (modifiable) copies.

Popularity 10/10 Helpfulness 2/10 Language cpp

Source: Grepper

Tags: c++

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Contributed on Dec 12 2021

alistair0111

0 Answers Avg Quality 2/10

auto in c++

Comment

int foo = 0;
auto bar = foo;  // the same as: int bar = foo; 
// type of bar is the type of the value used to initialize it

Popularity 10/10 Helpfulness 2/10 Language cpp

Source: cplusplus.com

Tags: auto

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Contributed on May 11 2021

Lazy Lyrebird

0 Answers Avg Quality 2/10

C++ auto&&

Comment

auto&& vec = some_expression_that_may_be_rvalue_or_lvalue;
auto i = std::begin(vec);
(*i)++;
//By using auto&& var = <initializer> you are saying: I will accept any initializer regardless of whether it is an lvalue or rvalue expression and I will preserve its constness

Popularity 7/10 Helpfulness 1/10 Language cpp

Source: stackoverflow.com

Tags: c++

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Contributed on Feb 03 2023

VARAK-VURAK

0 Answers Avg Quality 2/10

auto i cpp

Comment

auto n=1;
// this will make the type int, and you can't change trough the program;
cout << n;
// OR
auto n="how you doin'";
cout << n;

Popularity 10/10 Helpfulness 1/10 Language cpp

Source: Grepper

Tags: auto

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Contributed on Oct 05 2021

Healthy Hedgehog

0 Answers Avg Quality 2/10

c++ auto

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