std::ignore
Defined in header <tuple>
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const /*unspecified*/ ignore; |
(since C++11) (until C++17) |
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inline constexpr /*unspecified*/ ignore; |
(since C++17) | |
An object of unspecified type such that any value can be assigned to it with no effect. Intended for use with std::tie when unpacking a std::tuple, as a placeholder for the arguments that are not used.
Example
unpack a pair returned by set.insert(), but only save the boolean.
Run this code
#include <iostream> #include <string> #include <set> #include <tuple> int main() { std::set<std::string> set_of_str; bool inserted = false; std::tie(std::ignore, inserted) = set_of_str.insert("Test"); if (inserted) { std::cout << "Value was inserted successfully\n"; } }
Output:
Value was inserted successfully
See also
creates a tuple of lvalue references or unpacks a tuple into individual objects (function template) |