该程序将从用户那里获取浮点数和运算符，并执行所需的计算，并打印出结果。每次计算的结果将用作下一次计算的操作数。
因此，我不确定是否通过使用switch语句正确地执行了此操作？有更好的方法吗？也许通过使用do-while循环？我真的很困惑。
#include <iostream>
#include <iomanip>
using namespace std;
int main()
{
float firstOperand;
cout << "Enter a number: ";
cin >> firstOperand;
cout << endl;
cout << "Choose an instruction code: " << endl << endl;
cout << "1) (+) for addition. " << endl;
cout << "2) (*) for multiplication. " << endl;
cout << "3) (p) for power. " << endl;
cout << "4) (c) to clear the current result. " << endl;
cout << "5) (-) for subtraction. " << endl;
cout << "6) (/) for divison. " << endl;
cout << "7) (s) for square root. " << endl;
cout << "8) (q) to quit the program. " << endl << endl;
int choice;
cin >> choice;
cout << endl;
float secondOperand;
cout << "Enter the second number: ";
cin >> secondOperand;
cout << endl;
switch (choice)
{
case 1:
{
float resultOne = firstOperand + secondOperand;
cout << "The result of the calculation is " << resultOne << endl;
}
case 2:
{
float thirdOperand;
cout << "Enter another number ";
cin >> thirdOperand;
cout << endl;
cout << "Choose an instruction code: " << endl << endl;
cout << "1) (+) for addition. " << endl;
cout << "2) (*) for multiplication. " << endl;
cout << "3) (p) for power. " << endl;
cout << "4) (c) to clear the current result. " << endl;
cout << "5) (-) for subtraction. " << endl;
cout << "6) (/) for divison. " << endl;
cout << "7) (s) for square root. " << endl;
cout << "8) (q) to quit the program. " << endl << endl;
float resultTwo = resultOne + thirdOperand;
cout << "The result of the calculation is " << resultTwo << endl;
}
break;
}
system("pause");
return 0;
}
答案 0 :(得分：2)
尝试以下代码：
#include <iostream>
#include <math.h>
using namespace std;
int main(){
float firstOperand, secondOperand, result;
int choice, quit = 0;
cout << "Enter a number: ";
cin >> firstOperand;
cout << endl;
while (1){
cout << "The first operand is " << firstOperand << endl;
cout << "\nChoose an instruction code: " << endl;
cout << "1) (+) for addition. " << endl;
cout << "2) (*) for multiplication. " << endl;
cout << "3) (p) for power. " << endl;
cout << "4) (c) to clear the current result. " << endl;
cout << "5) (-) for subtraction. " << endl;
cout << "6) (/) for divison. " << endl;
cout << "7) (s) for square root. " << endl;
cout << "8) (q) to quit the program. " << endl << endl;
cin >> choice;
cout << endl;
if (choice == 8){
cout << "Quitting the program..." << endl;
break;
}
cout << "Enter the second number: ";
cin >> secondOperand;
cout << endl;
switch(choice){
case 1: result = firstOperand + secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 2: result = firstOperand * secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 3: result = pow(firstOperand, secondOperand);
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 4: result = 0;
cout << "The result has been cleared to " << result << endl;
cout << "Enter the first operand: ";
cin >> firstOperand;
cout << endl;
break;
case 5: result = firstOperand - secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 6: if(secondOperand){
result = firstOperand / secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
}
else{
cout << "Second operand is " << secondOperand << "Choose again!" << endl;
}
case 7: result = sqrt(secondOperand);
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
default:cout << "Invalid input. Enter again!" << endl;
break;
}
}
}
主代码包装在带有退出条件的无限while循环内。当用户希望时，break语句用于退出while循环。
注意：操作员输入的是数字而不是符号。如果要将符号用作输入，则必须将选择变量更改为char。
更新：以下代码用于字符输入。
#include <iostream>
#include <math.h>
using namespace std;
int main(){
float firstOperand, secondOperand, result;
int quit = 0;
char choice;
cout << "Enter a number: ";
cin >> firstOperand;
cout << endl;
while (1){
cout << "The first operand is " << firstOperand << endl;
cout << "\nChoose an instruction code: " << endl;
cout << "1) (+) for addition. " << endl;
cout << "2) (*) for multiplication. " << endl;
cout << "3) (p) for power. " << endl;
cout << "4) (c) to clear the current result. " << endl;
cout << "5) (-) for subtraction. " << endl;
cout << "6) (/) for divison. " << endl;
cout << "7) (s) for square root. " << endl;
cout << "8) (q) to quit the program. " << endl << endl;
cin >> choice;
cout << endl;
if (choice == 'q'){
cout << "Quitting the program..." << endl;
break;
}
cout << "Enter the second number: ";
cin >> secondOperand;
cout << endl;
switch(choice){
case '+': result = firstOperand + secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case '*': result = firstOperand * secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 'p': result = pow(firstOperand, secondOperand);
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case 'c': result = 0;
cout << "The result has been cleared to " << result << endl;
cout << "Enter the first operand: ";
cin >> firstOperand;
cout << endl;
break;
case '-': result = firstOperand - secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
case '/': if(secondOperand){
result = firstOperand / secondOperand;
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
}
else{
cout << "Second operand is " << secondOperand << "Choose again!" << endl;
}
case 's': result = sqrt(secondOperand);
cout << "The result of the calculation is " << result << endl;
firstOperand = result;
break;
default: cout << "Invalid input. Enter again!" << endl;
break;
}
}
}
答案 1 :(得分：2)
以下是代码中的一种可能版本：
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
int select_operation()
{
int choice;
cout << "Choose an instruction code: " << endl << endl;
cout << "1) (+) for addition. " << endl;
cout << "2) (*) for multiplication. " << endl;
cout << "3) (p) for power. " << endl;
cout << "4) (c) to clear the current result. " << endl;
cout << "5) (-) for subtraction. " << endl;
cout << "6) (/) for divison. " << endl;
cout << "7) (s) for square root. " << endl;
cout << "8) (q) to quit the program. " << endl << endl;
cin >> choice;
cout << endl;
return choice;
}
int main()
{
float secondOperand;
float firstOperand;
float thirdOperand;
float resultOne;
int choice;
cout << "Enter a number: ";
cin >> firstOperand;
cout << endl;
choice = select_operation();
if (choice == 8)
return 0;
else if(choice == 7)
secondOperand = .5;
else{
cout << "Enter the second number: ";
cin >> secondOperand;
}
cout << endl;
while(1)
{
switch (choice) {
case 1:
resultOne = firstOperand + secondOperand;
cout << "The result of the calculation is " << resultOne << endl;
break;
case 2:
resultOne = firstOperand * secondOperand;
cout << "The result of the calculation is " << resultOne << endl;
break;
case 3:
resultOne = pow(firstOperand,secondOperand);
cout << "The result of the calculation is " << resultOne << endl;
break;
case 4:
resultOne = 0;
cout << "The result of the calculation is " << resultOne << endl;
break;
case 5:
resultOne = firstOperand - secondOperand;
cout << "The result of the calculation is " << resultOne << endl;
break;
case 6:
if(secondOperand){
resultOne = firstOperand / secondOperand;
cout << "The result of the calculation is " << resultOne << endl;
}
break;
case 7:
resultOne = pow(firstOperand,secondOperand);
cout << "The result of the calculation is " << resultOne << endl;
break;
}
choice = select_operation();
if (choice == 8)
return 0;
else if(choice == 7)
secondOperand = .5;
else{
cout << "Enter another number ";
cin >> thirdOperand;
secondOperand = thirdOperand;
}
}
cout << endl;
firstOperand = resultOne;
return 0;
}
上面的代码首先接受两个输入，如果是选项8，则立即返回（退出程序）。如果运算是平方根，因为它是不接受第二个运算数的一元运算。 继续读取第三个操作数和运算符，直到要求停止。