std::generate
From cppreference.com
Defined in header <algorithm>
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template< class ForwardIt, class Generator > void generate( ForwardIt first, ForwardIt last, Generator g ); |
(1) | |
template< class ExecutionPolicy, class ForwardIt, class Generator > void generate( ExecutionPolicy&& policy, ForwardIt first, ForwardIt last, Generator g ); |
(2) | (since C++17) |
1) Assigns each element in range
[first, last)
a value generated by the given function object g
.2) Same as (1), but executed according to
policy
. This overload does not participate in overload resolution unless std::is_execution_policy_v<std::decay_t<ExecutionPolicy>> is trueParameters
first, last | - | the range of elements to generate | ||||||
policy | - | the execution policy to use. See execution policy for details. | ||||||
g | - | generator function object that will be called. The signature of the function should be equivalent to the following:
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 .
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Return value
(none)
Complexity
Exactly std::distance(first, last) invocations of g()
and assignments.
Exceptions
The overload with a template parameter named ExecutionPolicy
reports errors as follows:
- If execution of a function invoked as part of the algorithm throws an exception and
ExecutionPolicy
is one of the three standard policies, std::terminate is called. For any otherExecutionPolicy
, the behavior is implementation-defined. - If the algorithm fails to allocate memory, std::bad_alloc is thrown.
Possible implementation
template<class ForwardIt, class Generator> void generate(ForwardIt first, ForwardIt last, Generator g) { while (first != last) { *first++ = g(); } } |
Example
The following code fills a vector with random numbers:
Run this code
#include <algorithm> #include <iostream> #include <vector> #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
See also
copy-assigns the given value to every element in a range (function template) | |
assigns the results of successive function calls to N elements in a range (function template) |