是否有更短的方法來計算 C++ 中的 if (a == b || a == c)

Question

我想知道在 c++11 中是否可以計算：

if (a == b || a == c) {
    // do something
}

以更短更簡潔的方式，例如：

if (a == (b || c)) {
    // do something
}

（我知道上面的代碼行不通【它會計算是b還是c，然后檢查結果是否等於a】。我想知道之前是否有類似的方法來實現代碼： if (a == b || a == c) {} )

Answer 1

考慮：

#include <iostream>
#include <vector>

template <typename T>
bool operator==(const T t, std::vector<T> x) {
    for(const auto& v: x)
        if(t != v) {
            return false;
        }
    return true;
}

int main() {
    if ("s" == std::vector{"s", "s"}) {
        std::cout << "it's worked for two equal string\n";
    }

    if (!("s" == std::vector{"a", "s"})) {
        std::cout << "it's worked for two non-equal string\n";
    }

    if (1 == std::vector{1, 1}) {
        std::cout << "it's worked for two equal int\n";
    }
}

output 將是：

it's worked for two equal string
it's worked for two non-equal string
it's worked for two equal int