Comma separated floats in C++

Question

I am trying to separate a list of numbers such as: 34,45,12.3,100,34.6,50

I can do it only if there are no decimals like this:

#include <vector>
#include <string>
#include <sstream>
#include <iostream>

int main()
{
    std::string str = "34,45,12.3,100,34.6,50";
    std::vector<int> vect;

    std::stringstream ss(str);

    int i;

    while (ss >> i)
    {
        vect.push_back(i);

        if (ss.peek() == ',')
            ss.ignore();
    }

    for (i=0; i< vect.size(); i++)
        std::cout << vect.at(i)<<std::endl;

}

The problem here is with the decimals. The above will produce:

34 45 12 3 100 34 6 50

while it should produce:

34 45 12.3 100 34.6 50

basically the above code when it sees a dot '.' it acts as if it was a comma.

Any ideas?

You have a vector of `int` as in integer, thus it cannot hold a floating point number; they get truncated to the integer part. Change your vector so that its elements are floating point numbers. — bku_drytt, Apr 21 '16 at 03:02
This is a duplicate of http://stackoverflow.com/questions/1120140/how-can-i-read-and-parse-csv-files-in-c (but for some reason I don't think marking it as such, and closing it, would be right, here). — Sam Varshavchik, Apr 21 '16 at 03:06
You should learn the difference between integers and floating point numbers. A hint: Integers don't have fractional parts, so there is no decimal point. — Ken White, Apr 21 '16 at 03:08
Don't reuse variables! Declare two separate ones. (For instance, you reuse `i` inside your for loop.) — Mateen Ulhaq, Apr 21 '16 at 03:17
*"The above will produce: `34 45 12 3 100 34 6 50`"* - with which compiler/version, and language locale? I would normally expect it to produce only `34 45 12`, as the `.` in `12.3` should cause the `while (ss >> i)` loop to terminate, and indeed I get only `34 45 12` in testing on VS2013 / MSVC12 on Win7 set to English. — Tony Delroy, Apr 21 '16 at 03:53

score 3 · Answer 1 · answered Apr 21 '16 at 03:09

You should use a float and change the code to use float instead of int:

#include <vector>
#include <string>
#include <sstream>
#include <iostream>

int main()
{
    std::string str = "34,45,12.3,100,34.6,50";
    std::vector<float> vect;

    std::stringstream ss(str);

    float i;

    while (ss >> i)
    {
        vect.push_back(i);

        if (ss.peek() == ',')
        ss.ignore();
    }

    for (i=0; i< vect.size(); i++)
    std::cout << vect.at(i)<<std::endl;

}

score 3 · Answer 2 · edited Aug 18 '17 at 08:05

3

You should declare float i instead of int i and declare the vector as a vector of floats instead of a vector of integers. This is because 12.4 is not an integer, but a float.

edited Aug 18 '17 at 08:05

anc

171
1
18

answered Apr 21 '16 at 03:11

rox

435
4
16

score 1 · Accepted Answer · answered Apr 21 '16 at 03:08

I think your code interprets 12.3 as two different numbers because you haven't declared that number as a float. You vector holds all of the strings as integers, and not floats. If you declared your vectors as floats instead of integers, then your problem should be solved

Comma separated floats in C++

3 Answers3