C++替换字符串的一部分

Question

我的代码替换字符串"The number {0}大于{1}“中的{0}和{1}，0和1是变量参数列表的索引，但如果{}中添加了说明符，{0:说明符}，c表示货币，f表示固定，i表示int，e表示科学，则数字也是这样格式化的。只有在说明符相同、“数字{0:c}大于{1:c}”、“数字{0:c}大于{1:f}”、“数字{0:C}大于{1:F}”的情况下，代码才能工作，因此由于某种原因，结果都是以第二个索引的任何方式格式化的，在我给出的示例中，这两个索引都将被格式化为固定的。我不知道为什么第二个说明符会影响两个数字，值不会改变，但是第二个说明符会影响两个值。有人有什么想法吗？

我不明白这个问题，因为当程序到达行时

if(prompt.find(c2) != std::string::npos)

提示符已经修改过一次，所以应该只有一个{index:说明符}，因为第一个索引已经被替换了。我是不是开始这么想了？

#include <iostream>
#include <iomanip>
#include <string>
#include <cstdarg>
#include <sstream> 

using namespace std;

void write(string prompt, ...);
int ConvertCharToInt(char c);

void main()
{
    write("The number {0:[i]} is greater than {1:[i]}.\n", 5.9, 1.3, 4.7, 6.8);
}

void write(string prompt, ...)
{
char c1, c2;
int pos1, pos2, num1, num2, temp;
double arg1, arg2;

va_list arguments;
va_start(arguments, prompt);

pos1 = prompt.find_first_of("{");
c1 = prompt.at(pos1+1);
pos2 = prompt.find_last_of("{");
c2 = prompt.at(pos2+1);

num1 = ConvertCharToInt(c1);
num2 = ConvertCharToInt(c2);


for(int i = -1; i < num1; i++)
{
    arg1 = va_arg(arguments, double);
}   
for(int i = num1; i < num2; i++)
{
    arg2 = va_arg(arguments, double);
}

if(prompt.find(c1) != std::string::npos)
{
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream a;
        a << fixed << setprecision(2) << arg1;
        string r1 = "$" + a.str();

        size_t pos = prompt.find_first_of("{");
        prompt = prompt.replace(pos, 7, r1);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream a;
        a << scientific << arg1;
        string r1 = a.str();

        size_t pos = prompt.find_first_of("{");
        prompt = prompt.replace(pos, 7, r1);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {
        ostringstream a;
        a << fixed << setprecision(6) << arg1;
        string r1 = a.str();

        size_t pos = prompt.find_first_of("{");
        prompt = prompt.replace(pos, 7, r1);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream a;
        a << (int)(arg1+.5);
        string r1 = a.str();

        size_t pos = prompt.find_first_of("{");
        prompt = prompt.replace(pos, 7, r1);
    }
    else
    {
        ostringstream a;
        a << arg1;
        string r1 = a.str();

        size_t pos = prompt.find_first_of("{");
        prompt = prompt.replace(pos, 3, r1);
    }
}

if(prompt.find(c2) != std::string::npos)
{
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();

        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();

        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();

        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();

        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();

        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

cout << prompt << "\n";
va_end(arguments);
}

int ConvertCharToInt(char c)
{
int num;

switch(c)
{
    case '0':
        num = 0;
        break;
    case '1':
        num = 1;
        break;
    case '2':
        num = 2;
        break;
    case '3':
        num = 3;
        break;
    case '4':
        num = 4;
        break;
    case '5':
        num = 5;
        break;
    case '6':
        num = 6;
        break;
    case '7':
        num = 7;
        break;
    case '8':
        num = 8;
        break;
    case '9':
        num = 9;
        break;
    default:
        exit(EXIT_FAILURE);
}
return num;
}

Answer 1

问题是连续搜索您的标识符，如i、f等。

如果在结尾处有一个f string.find()，那么总是会找到f，然后留下If -否则分支。因此，因为f分支位于i分支之前，所以在示例中始终是f，并打印相应的格式。

解决办法是放弃寻找整个f表达式，而只寻找"[“。

Answer 2

实际上，我用它来处理这个问题，它非常长，也很乏味，但它很有效。

if(prompt.find("[c]") != std::string::npos)
{
    ostringstream a;
    a << fixed << setprecision(2) << arg1;
    string r1 = "$" + a.str();
    size_t pos = prompt.find_first_of("{");
    prompt = prompt.replace(pos, 7, r1);
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {   
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

else if(prompt.find("[e]") != std::string::npos)
{
    ostringstream a;
    a << scientific << arg1;
    string r1 = a.str();
    size_t pos = prompt.find_first_of("{");
    prompt = prompt.replace(pos, 7, r1);
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {   
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

else if(prompt.find("[f]") != std::string::npos)
{
    ostringstream a;
    a << fixed << setprecision(6) << arg1;
    string r1 = a.str();
    size_t pos = prompt.find_first_of("{");
    prompt = prompt.replace(pos, 7, r1);
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {   
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

else if(prompt.find("[i]") != std::string::npos)
{
    ostringstream a;
    a << (int)(arg1+.5);
    string r1 = a.str();
    size_t pos = prompt.find_first_of("{");
    prompt = prompt.replace(pos, 7, r1);
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {   
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

else
{
    ostringstream a;
    a << arg1;
    string r1 = a.str();
    size_t pos = prompt.find_first_of("{");
    prompt = prompt.replace(pos, 3, r1);
    if(prompt.find("[c]") != std::string::npos)
    {
        ostringstream s;
        s << fixed << setprecision(2) << arg2;
        string r2 = "$" + s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[e]") != std::string::npos)
    {
        ostringstream s;
        s << scientific << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[f]") != std::string::npos)
    {   
        ostringstream s;
        s << fixed << setprecision(6) << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else if(prompt.find("[i]") != std::string::npos)
    {
        ostringstream s;
        s << (int)(arg2+.5);
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
    else
    {
        ostringstream s;
        s << arg2;
        string r2 = s.str();
        size_t pos2 = prompt.find_last_of("{");
        prompt = prompt.replace(pos2, 7, r2);
    }
}

cout << prompt << "\n";