在字符串的最后一个字符中搜索标点符号

Searching the last character of a string for punctuation

本文关键字：搜索 标点符号 字符 最后一个 字符串      更新时间：2023-10-16

我目前正在制作一个小的文字处理器，但我遇到了一个问题。我正在尝试制作程序，以便当您按 Enter 时，程序会在您的输入上放置一个句号，然后是一个空格（我稍后会整理段落）。问题是我无法让程序搜索标点符号的最后一个字符，然后在结果上进行分支。编译器给了我以下错误：ISO C++禁止指针和整数之间的比较。我目前拥有的代码是： 

#include <fstream>
#include <string> 
#include <iostream>
#include <cstring>
#include <limits>
using namespace std ;
int main() 
{
int i = 0;
string text ;
string text2 ;
string title ;
string usertitle ;
string filelocation = "C:/Users/" ;
string user ;
string punctuation = ". : ! ? "
cout << "Input a title for your file: " ;
getline(cin , title) ;
title.insert(title.length() , ".txt" ) ;
cout << "Your title is: " << title << endl ;
cout << endl << "Input the username associated with your computer: " ;
getline(cin , user) ;
filelocation.append( user ) ;
filelocation.append("/Documents/") ;
filelocation.append(title) ;
cout << "Your chosen file name and location is: " << filelocation << endl ;
for ( i = 1 ; i > 0 ; i++ )
{
    if (text == "") 
    {
        cout << "There are a few instructions that you need to follow in order to use this system effectively: " << endl ;
        cout << "The first being that if you want to use it, you actually have to use a directory that exists. " << endl ;
        cout << "The second being that when you want to exit the program you press enter with nothing typed" << endl ;
        cout << "The third being NOT TO USE FULL STOPS, THE PROGRAM WILL PUT THEM IN FOR YOU" << endl ;
        cout << "Please begin writing: " << endl ;
        getline(cin,text) ;
    } 
    if (text!="")
    {
        text2.append(text) ; //<===HERE IS WHERE I AM HAVING TROUBLE
        if ((text.at(text.size() -1 ) != "!" ) && (text.at(text.size() -1 ) != "?") && (text.at(text.size() -1 ) != ":" )) 
        {
            text2.append(". ") ;
            getline(cin, text) ;
        }
        else
        {
            getline(cin, text) ;
        }
        if (text == "") 
        {
            cout << "End of session" << endl ; break ;
        }
    }
}
ofstream writer( filelocation.c_str() ) ;
if(! writer) 
{
    cout << "Error opening file for output: " << strerror(errno) << endl ;
    return -1 ;
}
else 
{
    writer << text2 << endl ;
    writer.close() ;
}
return 0 ;
}

提前感谢您的帮助！

"!"是一个

字符串，你想与一个字符进行比较：'!' .

您无法比较"!"和'!'。

我建议使用 rbegin() 来寻呼最后一个字符：

        text2.append(text.begin(), text.end());
        switch(*text.rbegin())
        {
            case '!': 
            case '?': 
            case ':': text2.append(". "); break;
        }
        getline(cin, text);
        if(text.empty())
        {
            cout << "End of session" << endl;
            break;
        }

if ((text.at(text.size() -1 ) != "!" ) && (text.at(text.size() -1 ) != "?") && (text.at(text.size() -1 ) != ":" ))

这既效率低下，又没有按照你的想法去做。 text.at(text.size() -1 )返回最后一个字符。 要获得您想要的：

char lastChar = text[text.size() - 1]; // or char lastChar = *text.rbegin();
if (!(lastChar == '.' || lastChar == '?' || lastChar == '!')) // note the single quotes
{
    text2.append(".  ");        
}
getline(cin, text);
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