我如何在 C 的结构定义中引入表达式？

Question

我定义了一个结构体：

struct Low {
     double high;
     double low;
     double fraction;   // = (Low.high - Low.low) / Low.high; 
     double percentage; // = Low.fraction * 100;  
} low2015, low2018, low2021, low2022;

这些评论暗示了我的意思。我想在结构体的定义块中引入一个表达式，Low这样我就不必手动进行my_struct.fractionand的赋值my_struct.percentage

low2021.high = 64854; 
low2021.low = 28805;
low2021.fraction = (low2021.high - low2021.low) / low2021.high;
low2021.percentage = low2021.fraction * 100;

对于所有四个变量，即low2015, low2018, low2021, low2022。我怎样才能做到这一点？

Answer 1

该结构足够小，可以按值返回。考虑添加一个功能MakeLow()。

struct Low {
     double high;
     double low;
     double fraction;
     double percentage;
};

static inline struct Low MakeLow(double high, double low) {
    return (struct Low) {
      .high = high,
      .low = low,
      .fraction = (high - low) / high,
      .percentage = (high - low) / high * 100,
    };
}

用法：

struct Low low2021 = MakeLow(64854, 28805);