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我正在做一个多项式计算器,我需要一些帮助,因为我将继续编写代码。

现在我只制作了 polinom 类,我将它表示为带有术语和一些函数的链表(现在只读取和打印多项式函数)。

这是目前只读取多项式并打印它的主程序:

#include "polinom.h"

int main()

{

polinom P1;
bool varStatus = false;
char var = '\0', readStatus = '\0';

cout << "P1 = ";
P1.read(readStatus, var, varStatus); // i don't need readStatus yet as i haven't implemented the reset and quit functions 

cout << "\n\nP = ";
P1.print(var);

getch();
return 0;
}

以及头文件polinom.h:

#ifndef _polinom_h
#define _polinom_h

#include <iostream>
#include <list>
#include <cstdlib>
#include <cctype>
#include <cstdio>
#include <conio.h>


using namespace std;

class polinom 
{
class term
{
    public:
        int coef;
        int pow;

        term() 
        {
            coef = 1;
            pow = 0;
        }    
};

list<term> poly;
list<term>::iterator i;

public:

    bool printable(char c) 
    {

        return (
                  ((int(c) > 42 && int(c) < 123) || isspace(c)) && int(c) != 44 && int(c) != 46 && int(c) != 47 && 
                  int(c) != 58 && int(c) != 59 && 
                  int(c) != 60 && int(c) != 61 && int(c) != 62 && int(c) != 63 && int(c) != 64 && int(c) != 65 && 
                  int(c) != 91 && int(c) != 92 && int(c) != 93 && int(c) != 95 && int(c) != 96
                ); 
    }


    void read(char &readStatus, char &var, bool &varStatus)
    {

        term t; // term variable to push it into the list of terms
        char c, lc, sign; // c = current char, lc = lastchar and sign the '+' or '-' sign before a coefficient
        int coef, pow; //variables to pass the coef and power to term t
        bool coefRead = false, powRead = false; //reading status of coef and power 

        while (c != '\r') { //we read characters until carriage return
            c = getch(); // get the new imputed char

            if (tolower(c) == 'r' || tolower(c) == 'q') { //if the user inputed r or q we reset the input or quit the program
                    readStatus = c; //pass current char value to readStatus so the program will know what to do next
                    return; //aborting the reading process
            }

            else 
            {
                if (printable(c)) cout << c; //print on screen only the correct characters

                if (!coefRead && !powRead) //we set term coef to the inputed value
                {                    
                    if (isdigit(c)) { 
                        if (isdigit(lc)) coef = coef * 10 + int(c); //if the last char was also a digit we multiply the last value of coef by 10 and add current char
                        else {                                    
                            if (sign == '-')  coef = -(int(c));//if the current coef has '-' before we set coef to it's negative value 
                            else              coef = int(c);   //this means a new term's coef is read
                    }
                    if (!isdigit(c) && isdigit(lc)) coefRead = true; //if the last char was a digit and we reached the var name we stop reading the coefficient
                }

                else if (coefRead && !powRead) //after coefficient is read we get the term's varname and power 
                {
                    if (isdigit(c)) { // just like in the case with coefficient we read the power until the current char is not a digit
                        if (isdigit(lc)) pow = pow * 10 + int(c);
                        else pow = int(c);
                    }

                    else if (isalpha(c) && isdigit(lc) && !varStatus) { //if the last char was a digit and the current not we reached the var name
                    var = c;                                            //also even though the variable is inputed more than once we save it only once
                    varStatus = true; //we mark the var name as read
                    }
                    else {
                        if (isdigit(lc)) powRead = true;
                    }   
                }

            else {
                if (c == '+' || c == '-') { // if a sign was inputed it means a new term is coming and we push the current term to the list and reset 
                    t.coef = coef;          // coefRead and powRead so we can read another term 
                    t.pow = pow;
                    poly.push_back(t);
                    sign = c;
                    coefRead = false;
                    powRead = false;
                }
            }

           lc = c; // we save the last character

            }
        } 
    }

    void print(char var)
    {
        for ( i=poly.begin() ; i != poly.end(); i++ ) { //going through the entire list to retrieve the terms and print them 

            if (i == poly.end() - 1) { // if we reached the last term 
                if (*(i->pow == 0) //if the last term's power is 0 we print only it's coefficient
                    cout << *(i->coef);
                else 
                    cout << *(i->coef) << var << "^" << *(i->pow); //otherwise we print both
            }

            else {
                if (*(i->coef > 0) //if the coef value is positive 
                    cout << *(i->coef) << var << "^" << *(i->pow) << " + "; //we also add the '+' sign
                else 
                    cout << *(i->coef) << var << "^" << *(i->pow) << " - "; // otherwise we add '-' sign
            }
        }
    }

};


#endif                    

编辑

多亏了 JonH,现在所有的编译错误都得到了修复,但是由于输入字符没有正确插入到列表中,读取功能不起作用。我知道这对你们来说可能微不足道,但如果你能帮助我,那就太好了。

谢谢!

4

4 回答 4

10

我在整个代码中发现很多缺少花括号和右括号。在花了几分钟修好其中至少 10 个之后,我想如果我帮助你学会钓鱼,而不是给你今晚的晚餐吃鱼,你会得到更好的服务。

你的代码写得像意识流。当您构建代码时,您的思维会跳来跳去,思考您需要构建的其他内容以及您刚刚编写的任何内容引入的新需求。当您想到这些事情时,您会去写它们并回到原来的位置。在不知不觉中,您已经编写了数百行代码,到处乱跳,到处写点。这样做的问题是,您不可能在不遗漏少量语法位的情况下继续处理这样的代码部分。

您应该采用更迭代的方法来编写代码。你如何做到这一点将有经验,但这里有一些指导:

  1. 首先用一些(最好是 1 个)核心方法和成员变量来存根类声明。
  2. 编译。你会得到链接器错误等,但你不应该得到任何语法错误,比如缺少括号或分号。在继续之前修复您找到的任何内容。
  3. 实现你刚刚存根的方法/函数。编译和修复非链接器错误。
  4. 当您想到在上述步骤中出现的次要或相关要求时,请在您的代码中编写注释,例如// TODO: Implement bool DoTheThing(int); 但不要实现它们。
  5. 循环回到第 1 步,尽可能保持你工作的范围有限和基本。在没有干净编译的情况下,永远不要超越编译步骤。

重复,直到你实现了一切。在此过程中,您可能会编译 50 次或更多。

于 2010-03-09T21:00:30.680 回答
2

你的根本问题是你写了一堆代码,没有逐个测试,没有考虑。当您作为初学者编写时,您应该尝试一次添加一点并确保它可以编译。即使作为高级程序员,模块化也是设计和代码编写过程中极其重要的一部分。

也就是说,这里有一些关于您发布的代码的提示:

  1. 您的功能printable丑陋至极,因此无法调试或理解。
  2. 嵌套if语句的数量表示设计缺陷。
  3. 您的if (isdigit(c))语句缺少一个结束括号。
  4. 在同一行声明(尤其是初始化)多个变量是不好的形式。
于 2010-03-09T20:45:59.900 回答
1

这些编译错误肯定在错误消息中具有与其关联的行号。您是否尝试查看指示的行以查看缺少的内容?如果这没有帮助,请发布编译器的完整错误输出,以便我们可以查看错误是什么。

于 2010-03-09T20:36:44.707 回答
1

您在 read 函数中缺少一些花括号。

我在这里重做了:

 void read(char &readStatus, char &var, bool &varStatus) 
{ 

    term t; // term variable to push it into the list of terms 
    char c, lc, sign; // c = current char, lc = lastchar and sign the '+' or '-' sign before a coefficient 
    int coef, pow; //variables to pass the coef and power to term t 
    bool coefRead = false, powRead = false; //reading status of coef and power  

    while (c != '\r') { //we read characters until carriage return 
        c = getch(); // get the new imputed char 

        if (tolower(c) == 'r' || tolower(c) == 'q') 
        { //if the user inputed r or q we reset the input or quit the program 
                readStatus = c; //pass current char value to readStatus so the program will know what to do next 
                return; //aborting the reading process 
        } 

        else  
        { 
            if (printable(c)) 
               cout << c; //print on screen only the correct characters 

            if (!coefRead && !powRead) //we set term coef to the inputed value 
            {                     
                if (isdigit(c)) 
                   {  
                    if (isdigit(lc)) 
                       coef = coef * 10 + int(c); //if the last char was also a digit we multiply the last value of coef by 10 and add current char 
                    else 
                      {                                     
                        if (sign == '-')  
                           coef = -(int(c));//if the current coef has '-' before we set coef to it's negative value  
                        else              
                           coef = int(c);   //this means a new term's coef is read 
                      } //end else 
                    }//end if isdigit(c)
                if (!isdigit(c) && isdigit(lc)) 
                   coefRead = true; //if the last char was a digit and we reached the var name we stop reading the coefficient 
            }  //end if

            else if (coefRead && !powRead) //after coefficient is read we get the term's varname and power  
            { 
                if (isdigit(c)) 
                   { // just like in the case with coefficient we read the power until the current char is not a digit 
                    if (isdigit(lc)) 
                       pow = pow * 10 + int(c); 
                    else 
                         pow = int(c); 
                    } 

                else if (isalpha(c) && isdigit(lc) && !varStatus) 
                     { //if the last char was a digit and the current not we reached the var name 
                         var = c;                                            //also even though the variable is inputed more than once we save it only once 
                          varStatus = true; //we mark the var name as read 
                     } 
                else 
                     { 
                     if (isdigit(lc)) 
                        powRead = true; 
                     }    
            } //end else if 

        else 
             { 
             if (c == '+' || c == '-') 
                { // if a sign was inputed it means a new term is coming and we push the current term to the list and reset  
                  t.coef = coef;          // coefRead and powRead so we can read another term  
                  t.pow = pow; 
                  poly.push_back(t); 
                  sign = c; 
                  coefRead = false; 
                  powRead = false; 
                } 
              } 

       lc = c; // we save the last character 

        } //end else
    }  //end while
} //end function

编辑

我还修复了打印功能:

 void print(char var) 
    { 
        for ( i=poly.begin() ; i != poly.end(); i++ ) { //going through the entire list to retrieve the terms and print them  

            if (i == poly.end()) { // if we reached the last term  
                if (i->pow == 0) //if the last term's power is 0 we print only it's coefficient 
                    cout << i->coef;
                else  
                    cout << i->coef << var << "^" << i->pow; //otherwise we print both 
            } 

            else { 
                if (i->coef > 0) //if the coef value is positive  
                    cout << i->coef << var << "^" << i->pow << " + "; //we also add the '+' sign 
                else  
                    cout << i->coef << var << "^" << i->pow << " - "; // otherwise we add '-' sign 
            } 
        } 
    } 
于 2010-03-09T20:48:02.830 回答