C++ 从 .txt 文件中读取浮点数
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Read floats from a .txt file
提问by degude
How can I read floats from a .txt file. Depending on the name at the begining of each line I want to read a different number of coordinates. The floats are seperated by "space".
如何从 .txt 文件中读取浮点数。根据每行开头的名称，我想读取不同数量的坐标。浮点数由“空格”分隔。
Example: triangle 1.2 -2.4 3.0
例子： triangle 1.2 -2.4 3.0
The result should be :
float x = 1.2 / float y = -2.4 / float z = 3.0
结果应该是：
float x = 1.2 / float y = -2.4 / float z = 3.0
The file has more lines with differens shapes which can be more complex but I think if i know how to do one of them I can do the others on my own.
该文件有更多不同形状的线条，这可能更复杂，但我想如果我知道如何做其中之一，我可以自己做其他的。
My Code so far:
到目前为止我的代码：
#include <iostream>
#include <fstream>
using namespace std;
int main(void)
{
ifstream source; // build a read-Stream
source.open("text.txt", ios_base::in); // open data
if (!source) { // if it does not work
cerr << "Can't open Data!\n";
}
else { // if it worked
char c;
source.get(c); // get first character
if(c == 't'){ // if c is 't' read in 3 floats
float x;
float y;
float z;
while(c != ' '){ // go to the next space
source.get(c);
}
//TO DO ?????? // but now I don't know how to read the floats
}
else if(c == 'r'){ // only two floats needed
float x;
float y;
while(c != ' '){ // go to the next space
source.get(c);
}
//TO DO ??????
}
else if(c == 'p'){ // only one float needed
float x;
while(c != ' '){ // go to the next space
source.get(c);
}
//TODO ???????
}
else{
cerr << "Unknown shape!\n";
}
}
return 0;
}
回答by Christian Rau
Why not just use C++ streams the usual way instead of all this getcmadness:
为什么不以通常的方式使用 C++ 流而不是所有这些getc疯狂的东西：
#include <sstream>
#include <string>
for(std::string line; std::getline(source, line); ) //read stream line by line
{
std::istringstream in(line); //make a stream for the line itself
std::string type;
in >> type; //and read the first whitespace-separated token
if(type == "triangle") //and check its value
{
float x, y, z;
in >> x >> y >> z; //now read the whitespace-separated floats
}
else if(...)
...
else
...
}
回答by dasblinkenlight
This should work:
这应该有效：
string shapeName;
source >> shapeName;
if (shapeName[0] == 't') {
float a,b,c;
source >> a;
source >> b;
source >> c;
}
