I have been having some problems with my code. I was asked to input elements from an .dat file into an array. For class we have to do this for various files without knowing how many elements will be in each file. The only thing we know is that here will never be more then 5000 elements per file.
One of my input file has the following elements:
5.675207 -0.571210
0.728926 0.666069
2.290909 0.751731 2.004545 0.907396
0.702893 0.646427 5.909504 -0.365045
2.082645 0.871841 5.597107 -0.633507
6.117769 -0.164663 6.091736 -0.190282
5.571074 -0.653433 4.503719 -0.978307
3.983058 -0.745620
3.670661 -0.504729
5.857438 -0.413001
When I run my code:
#define _CRT_NONSTDC_NO_DEPRECATE
#include <iostream>
#include <fstream>
#include <cstring>
using namespace std;
int main(int argc, char * argv[])
{
ifstream fin;
ofstream fout;
if (argc < 3)
{
cout << "Incorrect usage: prog.exe filenname number" << endl;
cout << "Exiting now, please try again." << endl;
return -1;
}
fin.open(argv[1]);
if (!fin)
{
cout << "Error opening file \"" << argv[1] << "\", exiting." << endl;
return -1;
}
fout.open(argv[2]);
int count = 0;
int word;
double points[5000];
while (fin >> word)
{
fin >> points[count];
++count;
}
fout << "Numer of points is: " << count/2 << endl;
for (int i = 0; i < count; i++)
{
fout << points[i] << " ";
}
fin.close();
fout.close();
return 0;
}
I outputted the elements just to make sure that they were properly inputted. I get the following and I don't know why.
0.675207 0.57121
0.728926 0.666069
0.290909 0.751731 0.004545 0.907396
0.702893 0.646427 0.909504 0.365045
0.082645 0.871841 0.597107 0.633507
0.117769 0.164663 0.091736 0.190282
0.571074 0.653433 0.503719 0.978307
0.983058 0.74562
0.670661 0.504729
0.857438 0.413001
The first digit is converted to a 0 for some reason and the negative ones become positive. Would anyone know why this is occurring?
int word;
is doing you no favours. First it's an integer so fin >> word only reads the integer portion of the inputs. 5.675207 is read as 5. the .675207 is left in the file stream for fin >> points[count]. Words isn't stored anywhere to the 5 is discarded but the .675207 lives on as 0.675207 in points[0].
Where the negative signs are going I didn't bother trying to figure out because
while (fin >> points[count])
{
++count;
}
fixes everything.
When you read in the numbers from the the file you are extracting them as "word" and then storing them as "points". "word" is an integer and "points" is a double, this will give you unexpected behavior. The compiler should give you warnings about this.
Related
Write and test a program that prompts the user to input a file name and a string to test for. Search the file for every occurrence of the specified string – when the string is found, display the line that contains it. When all occurrences of the string have been found display the number of times the string appeared in the file. Hint: You may use string member function find().
Here's my code, as I stated it works with some sentences but not all, it doesn't seem to have anything to do with the length either as if I repeat a line I know works, it won't run into any errors, can someone explain?
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <cctype>
using namespace std;
void find_common_words(string, int);
vector<string> words;
int main(){
vector<string> line;
string input;
char filename[50];
ifstream inputFile;
cout << "Enter File Name:" << endl;
cin.getline(filename, 50);
inputFile.open(filename);
//TESTING IF FILE IS OPEN
if (!inputFile.is_open()){
cout << "File Wasn't Opened!" << endl;
return 0;
}
while (getline(inputFile, input)){
line.push_back(input);
}
int size_of_array = static_cast<int>(line.size());
for (int i = 0; i < size_of_array; i++){
istringstream iss(line[i]);
int word_number = 0;
do {
string word;
iss >> word;
words.push_back(word);
word_number++;
} while (iss);
}
string commonword;
cout << "Enter a word to search for (without punctuation)" << endl;
cin >> commonword;
int size_of_array2 = static_cast<int>(words.size());
find_common_words(commonword, size_of_array2);
return 0;
}
void find_common_words(string search, int sizeofarray2) {
//CONVERSION TO STRING WITHOUT PUNCTUATION
for (int i = 0; i < sizeofarray2; i++){
string temp_string = words[i];
for (int j = 0, len = temp_string.size(); j < len; j++){
if (ispunct(temp_string[j])){
temp_string.erase(j--, 1);
len = temp_string.size();
}
}
words[i] = temp_string;
}
//SEARCHING FOR SAME WORDS
int line_number = 1;
int words_found = 0;
for (int i = 0; i < sizeofarray2; i++){
if (search == words[i]){
cout << search << " Was found on line " << line_number << endl;
words_found++;
}
if (words[i].length() == 0){
line_number++;
}
}
cout << line_number - 1 << " lines checked, " << words_found << " matches " << endl;
}
Heres my input file (randomly generated):
It's a very big deal.
Carl won the spelling bee and got a trophy!
Why is your cat so big?
Do you have a big bowl I can borrow?
It's a big company.
Penguins live in the Antarctica.
Don’t be silly, you're going to the game!
What are you talking about?
He threw up in the trash can!
You're so ratchet!
But she is a good caretaker.
Tom is looking for a bigger house to live in.
I get an error with Debug Assertion
Expression c> = -1 && c < = 255
I debugged the program and WhozCraig is right. In your input text in the line
Don’t be silly, you're going to the game!
In the word "Don’t", you do not have the normal apostrophe as you have in the word "It's" or "you're"
This special character is encoded as -110 in temp_string. In the description of std::ispunct you can read:
The behavior is undefined if the value of ch is not representable as unsigned char and is not equal to EOF.
-110 does not fit and causes a debug assertion error. If you cast it to unsigned char like WhozCraig proposed, it will work.
You can also fix your input file.
A very interesting and subtle error . . .
I am writing a code that reads an input file of numbers, sorts them in ascending order, and prints them to output. The only thing printed to output is some really freaky symbols.
Here is my code
#include <fstream>
#include <iostream>
using namespace std;
int main()
{
int i, y, temp, num[20];
char file_nameI[21], file_nameO[21];
ofstream outfile;
ifstream infile;
cout << "Please enter name of input file: ";
cin >> file_nameI;
infile.open(file_nameI);
if (!infile)
{
cout << "Could not open input file \n";
return 0;
}
cout << "Please enter name of output file: ";
cin >> file_nameO;
outfile.open(file_nameO);
if (!outfile)
{
cout << "Could not open output file \n";
return 0;
}
for (i = 0; i < 20; i++)
{
y = i + 1;
while (y < 5)
{
if (num[i] > num[y]) //Correction3
{
infile >> temp;
temp = num[i];
num[i] = num[y];
num[y] = temp;
//y++; //Correction4
}
y++;
}
}
for (i = 0; i < 5; i++)
outfile << "num[i]:" << num[i] << "\n";
return 0;
}
Here is my input
6 7 9 0 40
Here is the output
„Ô,üþ 54
H|À°ÀzY „Ô,üþ 0
Problems with your code are already mentioned in the comments but again:
First problem is uninitialized elements of num[20] - elements of num have indeterminate values so accessing any of them triggers undefined behavior. You should first read them from the file or at least initialize them to some default value.
The part of code that should most likely do the sorting is just completely wrong. If you'd like to implement your own function for sorting, you can pick up some well-known algorithm like e.g. quicksort - but C++ Standard Library already provides sorting function - std::sort.
Besides obvious mistakes:
You are using char[] - in C++ it's almost always better to use std::string.
Your static array can only store 20 values and you are reading those from a file. You can use std::vector which can grow when you add more elements than its current capacity. It also automatically fixes the problem with uninitialized elements of num[20].
As mentioned in the comments you can organize your code and improve readability by splitting it into functions.
Here you've got it quickly rewritten. This code uses std::string instead of char[], std::vector to store the numbers and std::sort. If there is something you don't understand here, read SO documentation:
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;
vector<int> read_file(ifstream& in_file)
{
vector<int> vec;
int value;
while (in_file >> value)
{
vec.push_back(value);
}
return vec;
}
void write_file(ofstream& out_file, const vector<int>& values)
{
for (size_t i = 0; i < values.size(); ++i)
out_file << "value #" << i << ": " << values[i] << '\n';
}
int main()
{
string input_filename, output_filename;
ofstream out_file;
ifstream in_file;
cout << "Please enter name of input file: ";
cin >> input_filename;
in_file.open(input_filename);
if (!in_file)
{
cout << "Could not open input file\n";
return 0;
}
cout << "Please enter name of output file: ";
cin >> output_filename;
out_file.open(output_filename);
if (!out_file)
{
cout << "Could not open output file\n";
return 0;
}
auto numbers = read_file(in_file);
sort(begin(numbers), end(numbers));
write_file(out_file, numbers);
return 0;
}
You might forgot to store values in num array. Just update your code as follows and it will work.
infile.open(file_nameI);
if (!infile){
cout << "Could not open input file \n";
return 0;
} else{
i = 0;
while (infile >> num[i]){
i++;
}
}
This program takes in an input, write it on a file character by character, count the amount of characters entered, then at the end copy it to an array of characters. The program works just fine until we get to the following snippet file.getline(arr, inputLength);. It changes the .txt file data and returns only the first character of the original input.
Any ideas?
#include <iostream>
#include <fstream>
using namespace std;
int getLine(char *& arr);
int main() {
char * arr = NULL;
cout << "Write something: ";
getLine(arr);
return 0;
}
int getLine(char *& arr) {
fstream file("temp.txt");
char input = '\0'; //initialize
int inputLength = 0; //initialize
if (file.is_open()) {
while (input != '\n') { //while the end of this line is not reached
input = cin.get(); //get each single character
file << input; //write it on a .txt file
inputLength++; //count the number of characters entered
}
arr = new char[inputLength]; //dynamically allocate memory for this array
file.getline(arr, inputLength); //HERE IS THE PROBLEM!!! ***
cout << "Count : " << inputLength << endl; //test counter
cout << "Array : " << arr << endl; //test line copy
file.close();
return 1;
}
return 0;
}
I see at least two problems with this code.
1) std::fstream constructor, by default, will open an existing file. It will not create a new one. If temp.txt does not exist, is_open() will fail. This code should pass the appropriate value for the second parameter to std::fstreams constructor that specifies that either a new file needs to be created, or the existing file is created.
Related to this: if the file already exists, running this code will not truncate it, so the contents of the file from this program's previous run will have obvious unexpected results.
2) The intent of this code appears to be to read back in the contents temp.txt that were previously written to it. To do that correctly, after writing and before reading it is necessary to seek back to the beginning of the file. This part appears to be missing.
There is no need in dynamic allocation because the std library functions get confused with mixed arguments such as cstring and pointer to cstring.I tested this code in Visual Studio 2015 compiler. It works good. Make sure to include all of the needed libraries:
#include <iostream>
#include <fstream>
#include<cstring>
#include<string>
using namespace std;
void getLine();
int main() {
cout << "Write something: ";
// no need to pass a pointer to a cstring
getLine();
system("pause");
return 0;
}
void getLine() {
char input[100]; // this is a cstring with
//a safe const number of elements
int inputLength; //to extract length of the actual input
//this function requires cstring as a first argument
// and constant length as a second
cin.get(input, 100, '\n'); //get each single character
//cast streamsize into int
inputLength = static_cast<int>(cin.gcount());
//testing input
cout << "Input: \n";
for (int i = 0; i < inputLength; i++)
{
cout << input[i];
}
cout << endl;
char arr[100];
strcpy_s(arr, input);
cout << "Count : " << inputLength << endl; //test counter
cout << "Array : " << endl; //test line copy
for (int i = 0; i < inputLength; i++)
{
cout << arr[i];
}
cout << endl;
// write cstring to a file
ofstream file;
file.open("temp.txt", ios::out);
if (file.is_open())
{
//write only what was entered in input
for (int i = 0; i < inputLength; i++)
file << arr[i];
file.close();
}
else cout << "Unable to open file";
}
I have two files. main.cpp:
#include <iostream>
#include <fstream>
using namespace std;
int main()
{
ifstream file;
file.open("file.txt");
if (!file.good()) {
cout << "Error." << endl;
return 1;
}
int n;
while (!file.eof()) {
file.clear();
file >> n;
if (!file.good() && !file.bad()) {
continue;
} else {
cout << "Hardware error." << endl;
break;
}
cout << n << endl;
}
file.close();
return 0;
}
and file.txt:
a 1 2 321b9 ac.de ef##g 5 #3
I'd like to read only integers from this file and write them out to the console. When file contains only integers program works well but when it contains any invalid characters then I get infinite loop. How can I fix that?
The loop is because the stream doesn't extract the character that is not an integer. You need to extract it before attempting to read another integer.
A small tweak could be all that is needed;
// on a failed read...
file.clear();
char dummy;
file >> dummy;
continue;
A side note on the use of while (!file.eof()); it is generally not recommended to do this. There are several Q&A on SO on this issue.
I have this program that changes negative numbers to positive in my file.
It works, but negative numbers in the file don't change.
for example, if I have this numbers in my file : 12 2 -3 -1
when I run the program, the sum of numbers will be 18, but when I open my file again, I see
12 2 -3 -1 . What should I do to see 12 2 3 1 ?
here is my code:
#include <iostream>
#include <fstream>
#include <string>
using namespace std;
int main()
{
string name;
cin >> name;
int number;
int num=0;
ifstream myFile(name, ios::in);
ofstream mine(name, ios::app);
while(myFile >> number)
{
num += (number<0 ? -number : number);
mine << num;
}
cout << "num = " << num << endl;
system("pause");
return 0;
}
Opening the file for reading and writing for the same time is generally not a bad idea. You probably got an I/O error during opening mine, but since you didn't check it, the program ignored your writes silently. Try reading the file contents first (to a vector for example), then close the file for reading and open again for writing (not appending, because that would leave the old contents in the file).
When writing the values back to the file, also write whitespace after the number, otherwise you'll just get a string of digits in the file but you won't know where one begins and another ends.
Your program now doesn't "change negative numbers to positive" but it prints the cumulative sum of absolute values to the file.
Try writing to the standard output first so you won't ruin your file while you are testing. If it works, then change cout to your output stream.
Here is the code.
#include <iostream>
#include <fstream>
#include <string>
#include <vector>
#include <cstdlib>
using namespace std;
int main()
{
string name;
cin >> name;
int number;
int num=0;
ifstream myFile(name, ios::in);
vector<int> vec;
while(myFile >> number)
{
vec.push_back(abs(number));
}
ofstream mine(name, ios::out);
for (vector<int>::iterator it = vec.begin(); it != vec.end(); ++it) {
num += *it;
mine << *it << " ";
}
cout << "num = " << num << endl;
return 0;
}
Opening a read and write file streams for the same file and process at the same time is inviting file corruption. Use ostringstream to store the values read from the file. The values
from the file are read, and the values stored in the ostringstream
buffer. The ifstream object is closed before re-opening the file with
an ofstream object so that the buffer contents can be saved.
Note the ios::app flag has been removed. Otherwise the new values
will append to the existing values.
abs() function is used to write back the absolute values - this
forces all values positive.
#include<sstream>
int main()
{
string name;
cin >> name;
int number;
int num=0;
ifstream myfile(name.c_str(), ios::in);
ostringstream oss;
while (myfile >> number)
{
num += (number<0 ? -number : number);
oss << abs(number) << " ";
}
myfile.close();
ofstream mine(name.c_str());
cout << "num = " << num << endl;
mine << oss.str();
return 0;
}
string name;
cin >> name;
int number=0;
int sum=0;
string outname=name+".pos.txt";
ifstream myFile(name,ifstream::in);
ofstream mine(outname, ofstream::out );
while(myFile >> number)
{
number= (number<0 ? -number : number);
sum+=number;
mine << number<<' ';
}
myFile.close();
mine.close();
cout << "sum = " << sum << endl;
system("pause");