Question

我刚刚用C ++开始了一个类，我们的第一个任务是使用用户提供的变量的简单代码。当我尝试编译代码时，我总是收到一些语法错误，但是根据有关该类的书（和其他在线资源），我认为我的语法是正确的。有见识吗？

编辑：为澄清起见，我意识到我的语法是错误的，因为编译器会抛出错误，我只是不确定自己在哪里错了。感谢收到的所有帮助。

代码：

//SP2019_Lab1Part2_Key.cpp

#include <iostream>
#include <string>
#include <sstream>
using namespace std;


cout << string(50, '-') << endl;
cout << "SP2019_Aaron Key - OUTPUT OF USING VARIABLES" << endl;
//declares string variable "Word"
char Word;
//Prompts user for word:
cout << "Word: ";
//Waits for input for value of "Word" from standard input (keyboard)
cin << Word;

//Declares integer variable "FirstNumber"
double FirstNumber;
//Prompts user for a number:
cout << "First Number: ";
//Waits for number:
cin << FirstNumber;

//Declares double variable "SecondNumber":
double SecondNumber;
//Prompts user for a number:
cout << "Second Number: ";
//Waits for input:
cin << SecondNumber;

//Adds FirstNumber and SecondNumber:
double SUM = FirstNumber + SecondNumber;
//Calculates Average of FirstNumber and SecondNumber:
double Avg = SUM / 2;


//Gives the average of FirstNumber and SecondNumber:
stringstream calavg;
calavg << "The average of " << FirstNumber << " and " << SecondNumber 
<< " is: " << Avg;
cout <<  char calavg.str();
cout << string(50, '-') << endl;

错误：

Microsoft (R) C/C++ Optimizing Compiler Version 19.16.27026.1 for x86
Copyright (C) Microsoft Corporation.  All rights reserved.

SP2019_Lab1Part2_Key.cpp
SP2019_Lab1Part2_Key.cpp(9): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(9): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(10): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(10): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(10): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'
SP2019_Lab1Part2_Key.cpp(14): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(14): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(14): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'
SP2019_Lab1Part2_Key.cpp(16): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(16): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(21): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(21): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(21): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'
SP2019_Lab1Part2_Key.cpp(23): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(23): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(23): error C2086: 'int cin': redefinition
SP2019_Lab1Part2_Key.cpp(16): note: see declaration of 'cin'
SP2019_Lab1Part2_Key.cpp(28): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(28): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(28): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'
SP2019_Lab1Part2_Key.cpp(30): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(30): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(30): error C2086: 'int cin': redefinition
SP2019_Lab1Part2_Key.cpp(16): note: see declaration of 'cin'
SP2019_Lab1Part2_Key.cpp(40): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(40): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(40): error C2371: 'calavg': redefinition; different basic types
SP2019_Lab1Part2_Key.cpp(39): note: see declaration of 'calavg'
SP2019_Lab1Part2_Key.cpp(41): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(41): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(41): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'
SP2019_Lab1Part2_Key.cpp(42): error C2143: syntax error: missing ';' before '<<'
SP2019_Lab1Part2_Key.cpp(42): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
SP2019_Lab1Part2_Key.cpp(42): error C2086: 'int cout': redefinition
SP2019_Lab1Part2_Key.cpp(9): note: see declaration of 'cout'

Answer 1

U在这里犯了一些错误：

您必须在int main()内编写整个主要代码
使用cin的语法是cin >>而不是cin <<
您不需要将char放在calavg.str()之前，因为它已经被声明为stringstream
请勿使用using namespace std。这是一种不良做法，可能会导致库冲突Why is "using namespace std" considered bad practice?

代码：

#include <iostream>
#include <string>
#include <sstream>

int main()
{
    std::cout << "SP2019_Aaron Key - OUTPUT OF USING VARIABLES" << std::endl;
    //declares string variable "Word"
    char Word;
    //Prompts user for word:
    std::cout << "Word: ";
    //Waits for input for value of "Word" from standard input (keyboard)
    std::cin >> Word;

    //Declares integer variable "FirstNumber"
    double FirstNumber;
    //Prompts user for a number:
    std::cout << "First Number: ";
    //Waits for number:
    std::cin >> FirstNumber;

    //Declares double variable "SecondNumber":
    double SecondNumber;
    //Prompts user for a number:
    std::cout << "Second Number: ";
    //Waits for input:
    std::cin >> SecondNumber;

    //Adds FirstNumber and SecondNumber:
    double SUM = FirstNumber + SecondNumber;
    //Calculates Average of FirstNumber and SecondNumber:
    double Avg = SUM / 2;


    //Gives the average of FirstNumber and SecondNumber:
    std::stringstream calavg;
    calavg << "The average of " << FirstNumber << " and " << SecondNumber 
    << " is: " << Avg;
    std::cout <<  calavg.str();

    return 0;
}

C ++的编译问题

1 个答案: