[编程入门]宏定义练习之三角形面积-题解（C语言代码）有返回值的宏定义

解题思路: 使用带返回值的宏    

注意事项:   1⃣️注意审题！保留三位小数！宏中的类型是否定义准确了！

                  2⃣️由于编写宏的时候编译器不会检查你的语法错误，所以我们一定要细心再细心地检查我们所定义的参数类型是否正确，是否正确添加分号等等，出现多个表达式的时候，建议使用反斜杠\分行。
参考代码:

                                            #include <stdio.h>

                                            #include <math.h>

                                            #define S(a,b,c) \

                                            ({float S_;\

                                            S_=( a + b + c ) / 2 ; S_;})

                                            #define A(s,a,b,c) ({float A_;\

                                            A_ =sqrt( s * ( s - a ) * ( s - b ) * ( s - c ) ); A_;})

                                            int main(){

                                                float a,b,c,s,area;

                                                scanf("%f%f%f",&a,&b,&c);

                                                s = S(a, b, c);

                                                area = A(s, a, b, c);

                                                printf("%.3f",area);

                                                return 0;

                                            }