Structured Bindings (C++17)

In a Nutshell

A single line of syntax that destructures the elements of a tuple, pair, struct, or array into independent variables at once, sparing you std::get and field-by-field access.

Header

None (language feature)

Core API Quick Reference

Binding Form	Syntax	Description
Bind by value	auto [a, b] = expr;	Copies the elements into new variables
Lvalue reference	auto& [a, b] = expr;	Binds references to the original object
Read-only reference	const auto& [a, b] = expr;	Const reference, avoids copying
Forwarding reference	auto&& [a, b] = expr;	Perfect forwarding semantics
Array destructuring	auto [a, b, c] = arr;	Binds to array elements (count must match)
Pair destructuring	auto [key, val] = *map_iter;	Binds to a pair's first/second
Tuple destructuring	auto [x, y, z] = tup;	Binds to get<I> of tuple-like types
Struct destructuring	auto [x, y] = point;	Binds to public data members (in declaration order)

Minimal Example

Expand codeCollapse23 lines

// Standard: C++17
#include <iostream>
#include <map>
#include <tuple>

struct Point { double x, y; };

int main() {
    // Struct destructuring
    Point p{1.0, 2.0};
    auto [px, py] = p;
    std::cout << px << ", " << py << "\n"; // 1, 2

    // Pair destructuring (map iteration)
    std::map<int, const char*> m{{1, "one"}, {2, "two"}};
    for (const auto& [key, val] : m) {
        std::cout << key << ": " << val << "\n";
    }

    // Tuple destructuring
    auto [a, b, c] = std::make_tuple(10, 20, 30);
    std::cout << a + b + c << "\n"; // 60
}

Embedded Applicability: High

• Pure compile-time syntactic sugar with zero runtime overhead; the generated code is fully equivalent to manual field access
• Simplifies unpacking multi-field structures such as register banks and sensor data, improving readability
• Combine with const auto& to avoid copies — ideal for read-only access to hardware-mapped structs
• Well supported in mainstream embedded toolchains (GCC 7+, ARM Clang 6+) since C++17

Compiler Support

GCC	Clang	MSVC
7	4.0	19.11

See Also

• Tutorial: Structured Bindings
• cppreference: Structured binding declaration

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