如何防止重複長右值

Question

int main() { 
    int x = 1, y = 2, z = 3, w = 4; 
#define formula x + y * z % w 
    x++; 
    do_something1(formula); 
    y++; 
    do_something2(formula); 
    z++; 
    do_something3(formula); 
    w++; 
    do_something4(formula); 
#undef formula 
    return 0; 
} 

我目前使用#define來防止重複長右值。有沒有更好的替代方法來做到這一點？

Answer 1

使用lambda表達：

int main() { 
    int x = 1, y = 2, z = 3, w = 4; 
    auto formula = [&] { return x + y * z % w; }; 
    x++; 
    do_something1(formula()); 
    y++; 
    do_something2(formula()); 
    z++; 
    do_something3(formula()); 
    w++; 
    do_something4(formula()); 
    return 0; 
}