函数指针数组

#include <stdio.h>// 加法
int addition(double num1, double num2, double *res);
// 减法
int subtraction(double num1, double num2, double *res);
// 乘法
int multiplication(double num1, double num2, double *res);
// 除法
int division(double num1, double num2, double *res);int main(void) {/** 定义加、减、乘、除四个函数* 用户键盘录入三个数字* 前两个表示参与计算的数字* 第三个数字表示调用的函数* */double num1;double num2;int calc;double answer;printf("输入需要计算的两个数字：");scanf("%lf %lf", &num1, &num2);printf("1) +\t2) -\t3) *\t4) /\t5) quit\n""输入需要的计算符号：");scanf("%d", &calc);int (*add)(double, double, double *) = addition;int (*sub)(double, double, double *) = subtraction;int (*mul)(double, double, double *) = multiplication;int (*div)(double, double, double *) = division;switch (calc) {case 1:add(num1, num2, &answer);printf("%lf + %lf = %lf\n", num1, num2, answer);break;case 2:sub(num1, num2, &answer);printf("%lf - %lf = %lf\n", num1, num2, answer);break;case 3:mul(num1, num2, &answer);printf("%lf * %lf = %lf\n", num1, num2, answer);break;case 4:if (div(num1, num2, &answer) == 1) {printf("除数不能为0！\n");} else {printf("%lf / %lf = %lf\n", num1, num2, answer);}break;default:printf("运算符无效！\n");break;}return 0;
}int addition(double num1, double num2, double *res) {*res = num1 + num2;return 0;
}int subtraction(double num1, double num2, double *res) {*res = num1 - num2;return 0;
}int multiplication(double num1, double num2, double *res) {*res = num1 * num2;return 0;
}int division(double num1, double num2, double *res) {if (num2 == 0) {return 1;}*res = num1 / num2;return 0;
}

#include <stdio.h>// 运算函数
int operate(double number1, double number2, char calc, double *answer);int main(void) {/** 定义一个运算函数* */double num1, num2, answer;char calc;printf("输入需要计算的两个数字：");scanf("%lf %lf", &num1, &num2);getchar();printf("1) +\t2) -\t3) *\t4) /\tq) quit\n""输入需要的计算符号：");scanf("%c", &calc);int flag = operate(num1, num2, calc, &answer);if (flag == 1) {printf("除数不能为0！\n");} else if (flag == -1) {printf("运算符无效！\n");} else {printf("%lf %c %lf = %lf\n", num1, calc, num2, answer);}return 0;
}int operate(double number1, double number2, char calc, double *answer) {switch (calc) {case '+':*answer = number1 + number2;break;case '-':*answer = number1 - number2;break;case '*':*answer = number1 * number2;break;case '/':if (number2 == 0) {return 1;}*answer = number1 / number2;break;default:return -1;}return 0;
}

#include <stdio.h>// 加法
int addition(double num1, double num2, double *res, char *calc);
// 减法
int subtraction(double num1, double num2, double *res, char *calc);
// 乘法
int multiplication(double num1, double num2, double *res, char *calc);
// 除法
int division(double num1, double num2, double *res, char *calc);int main(void) {/** 定义加、减、乘、除四个函数* 用户键盘录入三个数字* 前两个表示参与计算的数字* 第三个数字表示调用的函数* */// 函数指针数组int (*arr[4])(double, double, double *, char *) = {addition, subtraction,multiplication, division};double num1;double num2;int choose;double answer;char calc;printf("输入需要计算的两个数字：");scanf("%lf %lf", &num1, &num2);printf("1) +\t2) -\t3) *\t4) /\t5) quit\n""输入需要的计算符号：");scanf("%d", &choose);int flag = (arr[choose - 1])(num1, num2, &answer, &calc);if (flag == 1) {printf("除数不能为0！\n");} else {printf("%lf %c %lf = %lf\n", num1, calc, num2, answer);}return 0;
}int addition(double num1, double num2, double *res, char *calc) {*res = num1 + num2;*calc = '+';return 0;
}int subtraction(double num1, double num2, double *res, char *calc) {*res = num1 - num2;*calc = '-';return 0;
}int multiplication(double num1, double num2, double *res, char *calc) {*res = num1 * num2;*calc = '*';return 0;
}int division(double num1, double num2, double *res, char *calc) {if (num2 == 0) {return 1;}*res = num1 / num2;*calc = '/';return 0;
}