验证功能

Question

我的问题是如何验证getTestScore功能的数据？如果用户输入负数或数字超过100，则需要程序告诉用户invalid data, please enter a score in between 0 and 100。谢谢。

#include <iostream>
using namespace std;
//function prototypes
float getTestScore();
float calcAverage(float score1, float score2, float score3);
int main()
{
    float s1, s2, s3; //these variables are used to store test scores
    float average;
    //call getTestScore function to get the test scores
    s1 = getTestScore();
    s2 = getTestScore();
    s3 = getTestScore();
    //call calcAverage to calculate the average of three test scores
    average = calcAverage(s1, s2, s3);

    //display the average
    cout << "average of three test scores(" << s1 << "," << s2 << "," << s3 <<        ")is"     << average << endl;
    return 0;
}

//function definitions/implementation getTestScore function gets a test score from   the    user and
//validates the score to make sure the value is between 0 and 100. if score is out of range
//getTestScore function allows the user to re-enter the score. This function returns a valid score
// to the caller function
float getTestScore()
{
    float score = 0;
    do
    {
        cout << "Enter test score: " << endl;
        cin >> score;
    } while (!(score >= 0 && score <= 100));

    return score;
}

// calcAverage function calculates and returns the average of the three test  scores passed to
//the function as input.
float calcAverage(float score1, float score2, float score3)
{
    float average;
    average = (score1 + score2 + score3) / 3;

    return average;
}

Answer 1

在检查输入之前，通过使用“Do-While”至少执行一次代码块。

因此，您的条件不会检查第一个输入：

while (!(score >= 0 && score <= 100));

使用标准的while循环，因此事先检查这个条件可以解决您的问题。

Answer 2

您可以将while循环更改为：

float getTestScore()
{
    float score = 0;
    while ((cout << "Enter test score:  ")
                   && (!(cin >> score) || score < 0 || score > 100)) {
        // This part only gets executed on invalid input
        cout << "invalid data, please enter a score in between 0 and 100 ";
        cin.clear();
        cin.ignore(numeric_limits<streamsize>::max(), '\n');
    }
    return score;
}