std::generate - cppreference.com

##### cppreference.com

##### Search

Create account

##### Namespaces

- Page
- Discussion

##### Variants

##### Views

- View
- Edit
- History

##### Actions

# std::generate

From cppreference.com
< cpp‎ | algorithm

Defined in header `<algorithm>` |  |
template< class ForwardIt, class Generator > void generate( ForwardIt first, ForwardIt last, Generator g ); |  |

Assigns each element in range `[first, last)` a value generated by the given function object `g`.

### [edit] Parameters

first, last | - | the range of elements to generate
g | - | generator function object that will be called. The signature of the function should be equivalent to the following:
Ret fun(); |  |
The type Ret must be such that an object of type ForwardIt can be dereferenced and assigned a value of type Ret. ​
Type requirements
- `ForwardIt` must meet the requirements of `ForwardIterator`.

### [edit] Return value

(none)

### [edit] Complexity

Exactly std::distance(first, last) invocations of `g()` and assignments.

### [edit] Possible implementation

    template<class ForwardIt, class Generator>
    void generate(ForwardIt first, ForwardIt last, Generator g)
    {
        while (first != last) {
            *first++ = g();
        }
    }

### [edit] Example

The following code fills a vector with random numbers:

Run this code

    #include <algorithm>
    #include <iostream>
    #include <cstdlib>

    int main()
    {
        std::vector<int> v(5);
        std::generate(v.begin(), v.end(), std::rand); // Using the C function rand()

        std::cout << "v: ";
        for (auto iv: v) {
            std::cout << iv << " ";
        }
        std::cout << "\n";

        // Initialize with default values 0,1,2,3,4 from a lambda function
        // Equivalent to std::iota(v.begin(), v.end(), 0);
        int n = {0};
        std::generate(v.begin(), v.end(), [&n]{ return n++; });

        std::cout << "v: ";
        for (auto iv: v) {
            std::cout << iv << " ";
        }
        std::cout << "\n";
    }

Possible output:

    v: 52894 15984720 41513563 41346135 51451456
    v: 0 1 2 3 4

### [edit] See also

fill | assigns a range of elements a certain value (function template) [edit]
generate_n | saves the result of N applications of a function (function template) [edit]
std::experimental::parallel::generate (parallelism TS) | parallelized version of `std::generate` (function template) [edit]

Retrieved from "http://en.cppreference.com/mwiki/index.php?title=cpp/algorithm/generate&oldid=81174"