One function instead of const/non-const overload pairs (deducing this)

An explicit object parameter lets one function see whether it was called on a const object, replacing the duplicated overload pair.

#include <iostream>
#include <type_traits>

struct Counter {
    int n = 0;
    // One function instead of const/non-const overload pairs.
    void bump(this auto&& self) {
        if constexpr (std::is_const_v<std::remove_reference_t<decltype(self)>>) {
            std::cout << "read-only: n=" << self.n << '\n';
        } else {
            ++self.n;
            std::cout << "bumped: n=" << self.n << '\n';
        }
    }
};

int main() {
    Counter c;
    c.bump();
    const Counter d;
    d.bump();
}

Observed output:

bumped: n=1
read-only: n=0

Facts verified 2026-11-04. The code on this page was compiled and run on the box with GCC 16.2.0 at -std=c++23 -Wall -Wextra; the outputs quoted are the observed outputs. MSVC was not tested.

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