Rust 写过了的，还有个 C++ 版本。
最终代码
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| #include <iostream>
#include <cmath>
using namespace std;
void nya(double a, double b, double c) {
long double delta = (b * b) - (4.0 * a * c);
if (delta > 0.0) {
long double x1 = ((-b) + sqrt(delta)) / (2.0 * a);
long double x2 = ((-b) - sqrt(delta)) / (2.0 * a);
cout << "Two results: x1 = " << x1 << "; x2 = " << x2 << "." << endl;
}
if (delta == 0.0) {
long double x = (-b) / (2.0 * a);
cout << "One result: x = " << x << "." << endl;
}
if (delta < 0.0) {
cout << "No result." << endl;
}
}
int main() {
long double a, b, c;
char r;
while(true) {
cout << "Please input a = ";
cin >> a;
cout << "Please input b = ";
cin >> b;
cout << "Please input c = ";
cin >> c;
nya(a, b, c);
cout << "Continue?[Y/n]" << endl;
cin >> r;
if (r == 'n') {
break;
}
}
return 0;
}
|
细节
创建文件夹（
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| $ cd ~
$ mkdir cpp-quadratic-equation
$ cd cpp-quadratic-equation
$ touch a.cpp
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主函数部分
先创建一个main函数
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| int main() {
return 0;
}
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声明 a b c 变量
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| int main() {
long double a, b, c;
return 0;
}
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我想创建一个可重复的函数（与Rust版本的函数不同）。
如果用户希望重复计算过程，只需输入任何内容并按回车键，输入n退出。
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| int main() {
long double a, b, c;
char r;
while(true) {
cout << "Continue?[Y/n]" << endl;
cin >> r;
if (r == 'n') {
break;
}
}
return 0;
}
|
获取输入呐~
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| int main() {
long double a, b, c;
char r;
while(true) {
cout << "Please input a = ";
cin >> a;
cout << "Please input b = ";
cin >> b;
cout << "Please input c = ";
cin >> c;
cout << "Continue?[Y/n]" << endl;
cin >> r;
if (r == 'n') {
break;
}
}
return 0;
}
|
主运算函数部分
这个就不需要返回值了
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| void nya(double a, double b, double c) {
}
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声明delta变量
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| void nya(double a, double b, double c) {
long double delta = (b * b) - (4.0 * a * c);
}
|
逻辑判断部分
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| void nya(double a, double b, double c) {
long double delta = (b * b) - (4.0 * a * c);
if (delta > 0.0) {
long double x1 = ((-b) + sqrt(delta)) / (2.0 * a);
long double x2 = ((-b) - sqrt(delta)) / (2.0 * a);
cout << "Two results: x1 = " << x1 << "; x2 = " << x2 << "." << endl;
}
if (delta == 0.0) {
long double x = (-b) / (2.0 * a);
cout << "One result: x = " << x << "." << endl;
}
if (delta < 0.0) {
cout << "No result." << endl;
}
}
|
主运算函数完成了
合体！
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| void nya(double a, double b, double c) {
}
int main() {
while(true) {
nya(a, b, c);
cout << "Continue?[Y/n]" << endl;
cin >> r;
if (r == 'n') {
break;
}
}
return 0;
}
|
nya函数必须写在主函数前面，这是 C++ 标准的规定，要不不能调用（
调试
不同操作系统有不同的规矩，这里用 macOS + Clang 示例
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| $ clang++ a.cpp
$ ./a.out
|