range based for loop in c++

Loops  are the tools to make a instruction execute depends on how many times we want.

we all of us know loops in c++ are of three types :

• For loop
• while loop
• do while loop

syntax of for loop is simple :

for(initialisation statement  ;  test condition ; update statement)

{

       ... set of statements ;
}

OK , now you are clear here yet .

my question is  what is the output of the following code :

string var = "aayush";

for(char c : var)

{

  cout << c << " ";
}

output is :

  a a y u s h

that's here is the concept of range based for loop. 

when for loop terminates corresponding to some type of  list like array , string , vector with only a single condition as loop argument , then this type of for loop is called range based for loop.

According to c++ refrenece :

Executes a for loop over a range.

Used as a more readable equivalent to the traditional for loop operating over a range of values, such as all elements in a container.

 

syntax : 

for ( range_declaration : range_expression )

 

  loop_statement

example code :

// Illustration of range-for loop

// using CPP code

#include <iostream>

#include <vector>

#include <map>

//Driver

int main()

{

// Iterating over whole array

std::vector<int> v = {0, 1, 2, 3, 4, 5};

for (auto i : v)

std::cout << i << ' ';

std::cout << '\n';

// the initializer may be a braced-init-list

for (int n : {0, 1, 2, 3, 4, 5})

std::cout << n << ' ';

std::cout << '\n';

// Iterating over array

int a[] = {0, 1, 2, 3, 4, 5};

for (int n : a)

std::cout << n << ' ';

std::cout << '\n';

// Just running a loop for every array

// element

for (int n : a)

std::cout << "In loop" << ' ';

std::cout << '\n';

// Printing string characters

std::string str = "Geeks";

for (char c : str)

std::cout << c << ' ';

std::cout << '\n';

// Printing keys and values of a map

std::map <int, int> MAP({{1, 1}, {2, 2}, {3, 3}});

for (auto i : MAP)

std::cout << '{' << i.first << ", "

<< i.second << "}\n";

}