Thread: Read string convert and write

This doesn't sound like a good idea: you might lose accuracy reading the input as a float to begin with. Why not read the input as a string then write and apply a string_to_fixed function?

Oh, then where does fixed point come into play?

EDIT:
Oh, okay, I think I understand: 'write the converted value to a file named "file_out.txt"'. In that case, there's nothing more to do. Just write the integer as output. As simple as that. While you could convert the integer to string first, that would be unnecessary.

Originally Posted by bitslip

My function works on a floating point type numbers. So one way or another - I must convert the strings in the file (which represent floating point numbers) to type floats.

I thought that you were dealing with fixed point numbers, and were reading as float and then converting to fixed point for calculations.

Originally Posted by bitslip

Why should I do this on my own ?

Because if you're working with fixed point, then going through float first might introduce inaccuracy.

Originally Posted by bitslip

Do you expect my custom string to float conversion to work better than stof() ?

No, I expect your custom string to fixed point function to work better than stof followed by your float_to_fixed function if you were indeed dealing with fixed point rather than float.

However, if you aren't doing any floating point calculations, i.e., if the entire purpose of the program is to convert from one format to another, then the idea still applies: bypass float by reading as string, then convert directly to fixed point.

Originally Posted by bitslip

Someone sends me a text file that contains strings representing floating point values (as shown in the first post).
I need to convert these values to actual floating point numbers, apply my function that returns integer, convert these integers to strings and write them to a second file.
This second file will be used by an entirely different software that expects a file in that format...

I suggest that instead of "convert these integers to strings and write them to a second file", you write the integers to a second file, letting the ostream functionality do the conversion for you. For example:

Code:

int num = 123;
file_out << num;

Your input file is text, not binary.
If you need your output to be binary, what exactly is the format?
I've output to a text file below, one integer per line.
Never say ios::in for an ifstream or ios::out for an ofstream (that would be silly if you had to do that!).
ios::app doesn't make sense for an input-only file.
You may not want ios::app on your output file, either.

Code:

#include <iostream>
using namespace std;
 
int main()
{
    ifstream in("file_in.txt");
    ofstream out("file_out.txt");
    double x;
    while (in >> x)
        out << long(x * 100) << '\n'; // or however you convert them
}

Originally Posted by bitslip

Can you help me complete the code ?

It really isn't so hard:

Code:

// read string as float, apply function , write int as string
float x;
while (file_in >> x)
{
    file_out << float_to_fixed(x) << '\n';
}

But you didn't even bother to address john.c's points about ios::in etc.

Frankly, the above code might not work with your sample input file (I noticed a line of text that may be problematic), but I can't be bothered to fix it for you until you've shown that you're actually going to try out what people suggest.