Question

所以最近我开始学习我的第一语言C ++，并且我正在编写自己的程序来进行练习。为了让你知道我有多远，我刚刚被介绍给＆＃34;如果＆＃34;和＆＃34;否则如果＆＃34;课堂上的陈述。这是代码：

// Grade Calculator

#include<iostream>
#include<iomanip>
#include<cmath>
#include<string>

using namespace std;

int main()

{

float cutoffa, cutoffb, cutoffc, cutoffd, grade;
string firstname, lastname;

cout << setprecision(3) << fixed;
cout << "This program was made to test the \"if\" and \"else if\" statements.\n";
cout << "For this program you will be pretending to be a professor who is entering a student's grade.\n";
cout << "The first thing you will need to do is provide us with some basic information. Press enter when you are ready. \n";
cin.get();

cout << "What is the percent grade cut off (the lowest grade possible) for an A ? " ;
cin >> cutoffa;
cout << "What is the percent grade cut off for an B? " ;
cin >> cutoffb;
cout << "What is the percent grade cut off for an C? " ;
cin >> cutoffc;
cout << "What is the percent grade cut off for an D? " ;
cin >> cutoffd;
cout << "Enter the student's first name: ";
cin >> firstname;
cout << "Enter the student's last name: ";
cin >> lastname;
cout << "Enter the student's overall grade percentage: ";
cin >> grade;

if (grade >= cutoffa)
 cout << firstname << " " << lastname << "'s Final Grade is " << grade << "%, which is an A! Congrats!";
 else if (grade < cutoffa && grade >= cutoffb)
 cout << firstname << " " << lastname << "'s Final Grade is " << grade << "%, which is a B! Pretty good, could be better though.";
 else if (grade < cutoffb && grade >= cutoffc)
 cout << firstname << " " << lastname << "'s Final Grade is " << grade << "%, which is a C! You're average - nothing more and nothing less.";
 else if (grade < cutoffc && grade >= cutoffd)
 cout << firstname << " " << lastname << "'s Final Grade is " << grade << "% which is D! Damn, you're stupid";
 else if (grade < cutoffd)
 cout << firstname << " " << lastname << "'s Final Grade is " << grade << "% which is an F! Have you considered dropping out?";

cin.get();
cin.get();
return 0;
}

该程序应该是一个成绩计算器，它可以取得教师的成绩分类，并计算你是否在课堂上有A，B，C，D或F.我仅仅因为练习而做这件事，并且它与我的C ++课程没有任何关系。

它运行良好而且全部，但我已经发现了它的问题：接下来我接下来的代码行，它适用于所有条件语句（firstname和lastname是用户输入的字符串）他的名字/姓氏.cutoffa是用于接收用户输入的A的等级：

if (grade >= cutoffa) cout << firstname << " " << lastname << "'s Final Grade is " << grade << "%, which is an A! Congrats!";

问题在于，如果有人有像Jake Shams这样的名字，它会打印出来＆＃34; Jake Shams的最终成绩为98％，这是A！恭喜！＆＃34 ;.这里的错误是＆＃34; Shams＆＃34;＆＃34;因为它应该是＆＃34; Shams＆＃39;＆＃34;。就像我说的那样，我是初学者，这是我第一次使用if语句，所以如果有人可以向我解释如何获得它，那么如果用户的姓氏以字母S结尾，程序会在S之前添加一个撇号，像这样：Jake Shams'

Answer 1

使用if语句检查名称是否以s结尾。如果是，请将撇号添加到原始名称。如果没有，请添加。然后从你的cout语句中删除＆。

Answer 2

实际上， Jake Shams的是正确的，所以你不需要改变任何东西。

英语的一些变体写了 Jake Shams＆＃39; ，但是，正式地说，只有一个人为了复数而放弃了所有权 s （例如＆＃34;所有三头奶牛的脚都是数字的＆＃34; ）。

在没有正确的英语中，名称中的最终 s 完全被＆＃39> 取代（例如 Jake Sham＆＃39; ）但是，为了论证，你可以这样做：

if (grade >= cutoffa) {
     // Copy "lastname" and strip any terminating "s",
     // in advance of appending "'s" in a moment
     string lastname_possessive = lastname;
     if (lastname_possessive.back() == 's')
        lastname_possessive.pop_back();

     cout << firstname << " " << lastname_possessive << "'s Final Grade is "
          << grade << "%, which is an A! Congrats!";
}

但是，我稍微重写一下，以便lastname_possessive包含整个字。这种方式更可重用，意味着lastname_possessive变量本身就有意义。像这样：

if (grade >= cutoffa) {
     string lastname_possessive = lastname;
     if (lastname_possessive.back() == 's')
        lastname_possessive.pop_back();

     // Now do that appending
     lastname_possessive += "'s";

     cout << firstname << " " << lastname_possessive << " Final Grade is "
          << grade << "%, which is an A! Congrats!";
}

现在可以更轻松地更改此内容以呈现正确的英语：

if (grade >= cutoffa) {
     string lastname_possessive = lastname;
     if (lastname_possessive.back() == 's')
        lastname_possessive += "'";  // technically wrong but sometimes used
     else
        lastname_possessive += "'s";

     cout << firstname << " " << lastname_possessive << " Final Grade is "
          << grade << "%, which is an A! Congrats!";
}

实际上，您可能希望在条件之外执行此操作，以便在其他情况下也可以使用lastname_possessive。

Answer 3

我认为lastname的类型为std::string。然后，您可以询问if (lastname.back() == 's')。

Answer 4

你不应该成为一个＆＃34;＆＃39;＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;＆＃34;在一个名字之前的字母＆＃34; s＆＃34;是名字的一部分。

如果此人的姓名以＆＃34; s＆＃34;结尾？喜欢＆＃34;伯恩斯＆＃34;拥有＆＃34; Burn＆＃34;的程序代码是不对的。

无论如何 - 你可以创建一个字符串，存储它，并搜索＆＃34; S＆＃34;角色（位置）。

在旁注中 - 接受的编写变量名称的方法是使用名为＆＃34; CAMEL CASE＆＃34;这只是意味着你要写你的变量＆＃34; cutoffa＆＃34; as＆＃34; cutOffA＆＃34;。除了第一个单词之外，单词的每个首字母都大写。它将使您的代码更具可读性。如果您需要更多帮助，请告诉我。

初学者C ++帮助：if语句中的if语句

4 个答案: