C++17: Keep only some members when tuple unpacking

Solution 1:

Another alternative is to use an std::tie:

int b, c;
std::tie(std::ignore, b, c) = foo();

Edit

As mentioned in the comments, there are some issues with this approach:

• No type inference possible
• The objects must be constructed before, so unless the default constructors are trivial, it's not a good alternative.

Solution 2:

Unfortunately structured bindings do not explicitly support discarding members, and attributes such as [[maybe_unused]] cannot be applied to structured bindings (there's a proposal for that: P0609: "Attributes for Structured Bindings").

Here's a possible solution:

auto [a, b, c] = foo();
(void) a; // unused