Range-based for loop in C++ is added since C++ 11. It 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
Parameters :
range_declaration :
a declaration of a named variable, whose type is the
type of the element of the sequence represented by
range_expression, or a reference to that type.
Often uses the auto specifier for automatic type
deduction.
range_expression :
any expression that represents a suitable sequence
or a braced-init-list.
loop_statement :
any statement, typically a compound statement, which
is the body of the loop.
C++ implementation :
// 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 << '
'; // the initializer may be a braced-init-list for (int n : {0, 1, 2, 3, 4, 5}) std::cout << n << ' '; std::cout << '
'; // Iterating over array int a[] = {0, 1, 2, 3, 4, 5}; for (int n : a) std::cout << n << ' '; std::cout << '
'; // Just running a loop for every array // element for (int n : a) std::cout << "In loop" << ' '; std::cout << '
'; // Printing string characters std::string str = "Geeks"; for (char c : str) std::cout << c << ' '; std::cout << '
'; // 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 << "}
"; } |
Output:
0 1 2 3 4 5
0 1 2 3 4 5
0 1 2 3 4 5
In loop In loop In loop In loop In loop In loop
G e e k s
{1, 1}
{2, 2}
{3, 3}
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