std::generate is an STL algorithm, which is used to generate numbers based upon a generator function, and then, it assigns those values to the elements in the container in the range [first, last).
The generator function has to be defined by the user, and it is called successively for assigning the numbers.
Now, there can be a scenario, where we want to assign values only to the first n elements, for that we have another STL algorithm std::generate_n, which has the following syntax:
Template function:
OutputIterator generate_n (OutputIterator first, Size n, Generator gen); first: Output iterator pointing to the beginning of the container. n: No. of elements to be assigned a value, using generator function. gen: A generator function for generating the values. Returns: It doesnot have a void return type like std::generate, but, in fact, it returns an iterator pointing to the element that follows the last element whose value has been generated.
// C++ program to demonstrate the use of std::generate_n #include <iostream> #include <vector> #include <algorithm> // Defining the generator function int gen()
{ static int i = 0;
return ++i;
} using namespace std;
int main()
{ int i;
// Declaring a vector of size 10
vector< int > v1(10);
// using std::generate_n
std::generate_n(v1.begin(), 10, gen);
vector< int >::iterator i1;
for (i1 = v1.begin(); i1 != v1.end(); ++i1) {
cout << *i1 << " " ;
}
return 0;
} |
Output:
1 2 3 4 5 6 7 8 9 10