Member Avatar for power_computer

Ive used the search function just found one thing I needed more detailed help

I need to a read file of float numbers no more than 100 numbers but can be less than 100 into an array

I have made sample file contain 1 2 3

I have the following code

#include <iostream>
#include <fstream>
using namespace std; 

const int Max_Size = 100;

int main()
{
    ifstream inFile;
    float array[Max_Size];
    int i;
    string fileName;
    
    cout<<"Enter the name of the input: ";
    cin>>fileName; 
    
    inFile.open(fileName.c_str());
    
    for(i=0; i<Max_Size; i++)
    {        
          inFile>>array[i];
          cout<<array[i];
}
    
 
             
    inFile.close();

I also have to keep a counter of all numbers in the file

  • 2 Contributors
  • 4 Replies
  • 108 Views
  • 6 Hours Discussion Span
  • Latest Post Latest Post by power_computer

Dani AI

Generated

Good progress so far — pointed you to the right pattern (stop when extraction fails or when you hit your limit) and fixed the immediate printing bug by using an actual count. The “junk” was simply uninitialized array elements being printed because the print loop ran past the number of values actually read.

Avoid using eof() as the loop condition; the end‑of‑file flag is only set after a read fails, so it leads to subtle problems. Prefer testing the extraction itself (the operator>> result) to decide when to stop. See the reference for the extraction operator and eof() for details: operator>>, .

A safer, simpler approach is to use std::vector<float> and push back each successfully read value. This removes manual counting and avoids uninitialized slots:

#include <vector>
#include <fstream>
#include <iostream>

std::vector<float> values;
float x;
std::ifstream in("data.txt");
if (!in) return 1;
while (in >> x) values.push_back(x);
std::cout << "Read " << values.size() << " numbers\n";

For a 2-D layout (rows of space-separated floats), read the file line-by-line and parse each line with std::istringstream, collecting rows into std::vector<std::vector<float>>:

#include <sstream>
#include <string>

std::vector<std::vector<float>> table;
std::string line;
while (std::getline(in, line)) {
  std::istringstream iss(line);
  std::vector<float> row;
  float v;
  while (iss >> v) row.push_back(v);
  if (!row.empty()) table.push_back(std::move(row));
}

Final tips: always check the file opened successfully, use size_t for sizes, reserve(100) if you expect up to 100 elements, and print only up to the container’s size(). For parsing nuances and stream behavior see std::istringstream and std::vector::push_back.

Recommended Answers

All 4 Replies

Member Avatar for Ancient Dragon

That for loop is incorrect. What you want is to read until either Max_Size has been read or until end-of-file

int i = 0;
while(i < Max_Size && inFile>>array[i] )
   ++i;
Member Avatar for power_computer

Thanks and then I use the for loop to display the data?


If i use the for loop it displays the numbers but then a bunch of junk afterward ? i only have 3 float numbers in there atm

Member Avatar for Ancient Dragon

you need to post that code. Make sure the loop does not increment past the number of floats that were read, not Max_Size. The value of i in the loop I posted is the number of floats read.

for(int j = 0; j < i; j++)
{
   // blabla
}
Member Avatar for power_computer

Thanks! Works like a charm

here is my code so you dont think I was bumming you for answers
and changed i to the number of floats read and i to the array

#include <iostream>
#include <fstream>
using namespace std; 

const int Max_Size = 100;

int main()
{
    ifstream inFile;
    float array[Max_Size];
    int amountRead = 0, i;
    string fileName;
    
    cout<<"Entner the name of the input: ";
    cin>>fileName; 
    
    inFile.open(fileName.c_str());
    
    while(!inFile.eof() && inFile>>array[amountRead])
    {
                     amountRead++;
                     
                     }
    
    for(i=0; i<amountRead; i++)
    {
             cout<<array[i];
             }
    
  
  
   
    return 0;
}

Any idea how I would implement this into an 2-D Array

Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.