I am trying to do a problem using dynamic programming to find which items to select from a text file under a certain weight capacity while maximizing value. The file is in the format:
item1, weight, value
item2, weight, value
With a variable number of items. I am having a problem reading the file in the main method, where I am trying to error check for bad input. My problem comes from when I check if the weight is either missing, or is a string instead of an int. I can't figure out how to check separately for a string or if there is nothing in that spot. I am supposed to output a different error depending on which it is. Thanks.
int main(int argc, char * const argv[])
{
std::vector<Item> items;
if (argc != 3)
{
std::cerr << "Usage: ./knapsack <capacity> <filename>";
return -1;
}
int capacity;
std::stringstream iss(argv[1]);
if (!(iss >> capacity) || (capacity < 0))
{
std::cerr << "Error: Bad value '" << argv[1] << "' for capacity." << std::endl;
return -1;
}
std::ifstream ifs(argv[2]);
if (ifs.is_open())
{
std::string description;
unsigned int weight;
unsigned int value;
int line = 1;
while (!ifs.eof())
{
if (!(ifs >> description))
{
std::cerr << "Error: Line number " << line << " does not contain 3 fields." << std::endl;
return -1;
}
if (!(ifs >> weight))
{
if (ifs.eof())
std::cerr << "Error: Line number " << line << " does not contain 3 fields." << std::endl;
else
std::cerr << "Error: Invalid weight '" << ifs << "' on line number " << line << "." << std::endl;
return -1;
}
else if (!(ifs >> weight) || (weight < 0))
{
std::cerr << "Error: Invalid weight '" << ifs << "' on line number " << line << "." << std::endl;
return -1;
}
if (!(ifs >> value))
{
if (ifs.eof())
std::cerr << "Error: Line number " << line << " does not contain 3 fields." << std::endl;
else
std::cerr << "Error: Invalid value '" << ifs << "' on line number " << line << "." << std::endl;
return -1;
}
else if (!(ifs >> value) || (value < 0))
{
std::cerr << "Error: Invalid value '" << ifs << "' on line number " << line << "." << std::endl;
return -1;
}
Item item = Item(line, weight, value, description);
items.push_back(item);
line++;
}
ifs.close();
knapsack(capacity, items, items.size());
}
else
{
std::cerr << "Error: Cannot open file '" << argv[2] << "'." << std::endl;
return -1;
}
return 0;
}
I think better approach will be using getline function, by which you will take a whole line and then you can try to split it into three strings. If three parts are not found or any of the three parts is not in a right format you can output an error.
An example code is give below,
#include<fstream>
#include<iostream>
#include<vector>
#include <sstream>
#include<string>
using namespace std;
void split(const std::string &s, std::vector<std::string> &elems, char delim) {
elems.clear();
std::stringstream ss(s);
std::string item;
while (std::getline(ss, item, delim)) {
elems.push_back(item);
}
}
int main()
{
vector<string> elems;
ifstream fi("YOUR\\PATH");
string inp;
while(getline(fi, inp))
{
split(inp, elems, ' ');
if(elems.size() != 3)
{
cout<<"error\n";
continue;
}
int value;
bool isint = istringstream(elems[1])>>value;
if(!isint)
{
cout << "error\n";
continue;
}
cout<<"value was : " << value << endl;
}
return 0;
}
You could read the whole line at once and check it's format using regular expressions.
Related
I'm making a very simple file parser, in CSV style. The compilation runs smoothly, and when I run it, I'm having a segfault (core dumped). The only printed line is the one telling "Done" to say that the file succesfully opened. So my guess is that the Segfault happened during while(getline(myfile, line)).
Here's my code (parser.cpp):
#include "parser.h"
vector<string> str_explode(string const & s, char delim)
{
vector<string> result;
istringstream iss(s);
for (string token; getline(iss, token, delim); )
{
result.push_back(move(token));
}
return result;
}
vector<vector<string>> getTokensFromFile(string fileName)
{
bool verbose = true;
if(verbose)
cout << "Entering getTokensFromFile(" << fileName << ")" << endl ;
/* declaring what we'll need :
* string line -> the line beeing parsed
* ifstream myfile -> the file that name has been given as parameter
* vector <vector <string> > tokens -> the return value
*
* Putting all line into tokens
*/
string line;
ifstream myfile(fileName);
vector< vector<string> > tokens;
if(verbose)
cout << "Opening file " << fileName << " ... ";
if (myfile.is_open())
{
if(verbose)
cout << "Done !" << endl;
while (getline (myfile,line))
{
if(verbose)
cout << "Parsing line '" << line << "'. ";
// If line is blank or start with # (comment)
// then we don't parse it
if((line.length() == 0) || (line.at(0) == '#'))
{
if(verbose)
cout << "Empty or comment, passing.";
continue;
}
else
{
vector <string> tmptokens;
if(verbose)
cout << "Adding token " << tmptokens[0] << " and its values.";
tokens.push_back(tmptokens);
}
cout << endl;
}
}
else
{
cout << "Unable to open file " << fileName << endl;
throw exception();
}
if(verbose)
cout << "Exiting getTokensFromFile(" << fileName << ")" << endl;
return tokens;
}
main.cpp
#include "parser.h"
int main()
{
getTokensFromFile("testfile.csv");
return 0;
}
And my testfile.csv
version;1.3
###### SPECIE ######
SpecieID;Value1
VariantID;Value2
####################
##### IDENTITY #####
Name;Value3
DOName;Value4
####################
All files are in the same folder.
Do you have any clue why I'm having this segfault?
Thanks
Here is one obvious error, where you are accessing a vector's element out-of-bounds. Accessing an out-of-bounds element is undefined behavior.
else
{
vector <string> tmptokens;
if(verbose)
cout << "Adding token " << tmptokens[0] << " and its values.";
tokens.push_back(tmptokens);
}
Since tmptokens is empty, there is no tmptokens[0].
If the vector is empty, you could have done this:
else
{
if(verbose)
cout << "Adding new token and its values.";
tokens.push_back({});
}
There is no need to manually create an empty vector starting with C++11.
I'm writing a simple encryption program in C++ to encrypt a text-based file.
It's using a simple XOR cipher algorithm, but this produces ASCII control characters in the output file. When I try to read from the newly encrypted file with std::ifstream, it stumbles upon character #26, it stops and becomes unable to read the rest of the file.
Example if I try to encrypt this text:
This is just a simple sample
text with two rows and one sentence.
It turns it to this
/[[[[[
[[[ [[[U
When I try to read that file in my program, it can't read past the character at position 15, so I get a half encrypted file.
How can I fix this?
Here's the code:
#include <iostream>
#include <Windows.h>
#include <string>
#include <fstream>
void Encrypt(char encryptionKey, std::string filename)
{
std::ifstream sourceFile(filename);
std::ofstream outputFile(filename.substr(0, filename.find_last_of("\\")) + "\\Encrypted" + filename.substr(filename.find_last_of("\\") + 1), std::ofstream::out | std::ofstream::trunc);
std::string sourceLine;
std::string outputLine;
long numLines = 0;
if (sourceFile.is_open())
{
std::cout << "Opening file: " + filename + " for encryption" << std::endl;
while (sourceFile.good()) // This iterates over the whole file, once for each line
{
sourceLine = ""; //Clearing the line for each new line
outputLine = ""; //Clearing the line for each new line
std::getline(sourceFile, sourceLine);
for (int i = 0; i < sourceLine.length(); i++) // Looping through all characters in each line
{
char focusByte = sourceLine[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
outputLine.push_back(focusByte);
//std::cout << sourceLine << std::flush;
}
numLines++;
outputFile << outputLine << std::endl;
}
}
sourceFile.close();
outputFile.close();
}
void Decrypt(unsigned int encryptionKey, std::string filename)
{
std::ifstream sourceFile(filename);
std::ofstream outputFile(filename.substr(0, filename.find_last_of("\\")) + "\\Decrypted" + filename.substr(filename.find_last_of("\\") + 1), std::ofstream::out | std::ofstream::trunc);
std::string sourceLine;
std::string outputLine;
long numLines = 0;
if (sourceFile.is_open())
{
std::cout << "Opening file: " + filename + " for decryption" << std::endl;
while (sourceFile.good()) // This iterates over the whole file, once for each line
{
if (sourceFile.fail() == true)
std::cout << "eof" << std::endl;
sourceLine = ""; //Clearing the line for each new line
outputLine = ""; //Clearing the line for each new line
std::getline(sourceFile, sourceLine);
for (int i = 0; i < sourceLine.length(); i++) // Looping through all characters in each line
{
char focusByte = sourceLine[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
outputLine.push_back(focusByte);
}
numLines++;
outputFile << outputLine << std::endl;
}
}
sourceFile.close();
outputFile.close();
}
int main(int argument_count,
char * argument_list[])
{
system("color a");
std::string filename;
if (argument_count < 2)
{
std::cout << "You didn't supply a filename" << std::endl;
}
else
{
filename = argument_list[1];
std::cout << "Target file: " << filename << std::endl;
std::cout << "Press e to encrypt the selected file, Press d to decrypt the file > " << std::flush;
char choice;
while (true)
{
std::cin >> choice;
if (choice == 'e')
{
Encrypt(123, filename);
break;
}
else if (choice == 'd')
{
Decrypt(123, filename);
break;
}
else
{
std::cout << "please choose option e or d for encryption respectivly decryption" << std::endl;
}
}
}
std::cout << "\nPaused, press Enter to continue > " << std::flush;
system("Pause");
return EXIT_SUCCESS;
}
In Decrypt(), after the first call to std::getline(), sourceFile.good() is false and sourceFile.fail() is true, which is why you stop reading subsequent lines from the encrypted file.
The reason is because the encrypted file has an encoded 0x1A byte in it, and depending on your platform and STL implementation, that character likely gets interpreted as an EOF condition, thus enabling the std::ifstream's eofbit state, terminating further reading.
In my compiler's STL implementation on Windows, when std::ifstream reads from a file, it ultimately calls a function named _Fgetc():
template<> inline bool _Fgetc(char& _Byte, _Filet *_File)
{ // get a char element from a C stream
int _Meta;
if ((_Meta = fgetc(_File)) == EOF) // <-- here
return (false);
else
{ // got one, convert to char
_Byte = (char)_Meta;
return (true);
}
}
When it tries to read an 0x1A character, fgetc() returns EOF, and when _Fgetc() returns false, std::getline() sets the eofbit on the std::ifstream and exits.
Check your compiler's STL for similar behavior.
This behavior is because you are opening the encrypted file in text mode. You need to open the encrypted file in binary mode instead:
std::ifstream sourceFile(..., std::ifstream::binary);
Also, you should enable binary mode on the encrypted file in Encrypt() as well:
std::ofstream outputFile(..., std::ofstream::binary | std::ofstream::trunc);
Try something more like this instead:
#include <Windows.h>
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
void Encrypt(char encryptionKey, const std::string &filename)
{
std::string::size_type pos = filename.find_last_of("\\");
std::string out_filename = filename.substr(0, pos+1) + "Encrypted" + filename.substr(pos + 1);
std::ifstream sourceFile(filename.c_str());
std::ofstream outputFile(out_filename.c_str(), std::ofstream::binary | std::ofstream::trunc);
if (sourceFile.is_open())
{
std::cout << "Opened file: " + filename + " for encryption" << std::endl;
std::string line;
long numLines = 0;
while (std::getline(sourceFile, line)) // This iterates over the whole file, once for each line
{
for (std::string::size_type i = 0; i < line.length(); ++i) // Looping through all characters in each line
{
char focusByte = line[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
line[i] = focusByte;
//std::cout << line << std::flush;
}
outputFile << line << std::endl;
++numLines;
}
}
}
void Decrypt(char encryptionKey, const std::string &filename)
{
std::string::size_type pos = filename.find_last_of("\\");
std::string out_filename = filename.substr(0, pos+1) + "Decrypted" + filename.substr(pos + 1);
std::ifstream sourceFile(filename.c_str(), std::ifstream::binary);
std::ofstream outputFile(out_filename.c_str(), std::ofstream::trunc);
if (sourceFile.is_open())
{
std::cout << "Opened file: " + filename + " for decryption" << std::endl;
std::string line;
long numLines = 0;
while (std::getline(sourceFile, line)) // This iterates over the whole file, once for each line
{
for (std::string::size_type i = 0; i < line.length(); ++i) // Looping through all characters in each line
{
char focusByte = line[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
line[i] = focusByte;
}
outputFile << line << std::endl;
++numLines;
}
std::cout << "eof" << std::endl;
}
}
int main(int argument_count, char* argument_list[])
{
std::system("color a");
std::string filename;
if (argument_count < 2)
{
std::cout << "Enter a file to process: " << std::flush;
std::getline(std::cin, filename);
}
else
{
filename = argument_list[1];
}
if (filename.empty())
{
std::cout << "You didn't supply a filename" << std::endl;
return EXIT_FAILURE;
}
std::cout << "Target file: " << filename << std::endl;
std::cout << "Press e to encrypt the file" << std::endl;
std::cout << "Press d to decrypt the file" << std::endl;
char choice;
while (true)
{
std::cout << "> " << std::flush;
std::cin >> choice;
if (choice == 'e')
{
Encrypt(123, filename);
break;
}
else if (choice == 'd')
{
Decrypt(123, filename);
break;
}
else
{
std::cout << "please choose option e or d for encryption or decryption, respectively" << std::endl;
}
}
std::cout << std::endl << "Paused, press Enter to continue" << std::flush;
std::system("pause");
return EXIT_SUCCESS;
}
That being said, keep in mind that when using XOR, some of the encrypted characters might end up being \r (0x0D) or \n (0x0A), which will interfere with std::getline() when decrypting the file later on, producing a decrypted output that does not match the original text input.
Since you should be treating the encrypted file as binary, you should not be reading/writing the file as text at all. Choose a different format for your encrypted output that does not rely on line-break semantics in text vs binary mode.
For example:
#include <Windows.h>
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>
void Encrypt(char encryptionKey, const std::string &filename)
{
std::string::size_type pos = filename.find_last_of("\\");
std::string out_filename = filename.substr(0, pos+1) + "Encrypted" + filename.substr(pos + 1);
std::ifstream sourceFile(filename.c_str());
std::ofstream outputFile(out_filename.c_str(), std::ofstream::binary | std::ofstream::trunc);
if (sourceFile.is_open())
{
std::cout << "Opened file: " + filename + " for encryption" << std::endl;
std::string line;
std::string::size_type lineLen;
long numLines = 0;
while (std::getline(sourceFile, line)) // This iterates over the whole file, once for each line
{
lineLen = line.length();
for (std::string::size_type i = 0; i < lineLen; ++i) // Looping through all characters in each line
{
char focusByte = line[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
line[i] = focusByte;
//std::cout << line << std::flush;
}
outputFile.write((char*)&lineLen, sizeof(lineLen));
outputFile.write(line.c_str(), lineLen);
++numLines;
}
}
}
void Decrypt(char encryptionKey, const std::string &filename)
{
std::string::size_type pos = filename.find_last_of("\\");
std::string out_filename = filename.substr(0, pos+1) + "Decrypted" + filename.substr(pos + 1);
std::ifstream sourceFile(filename.c_str(), std::ifstream::binary);
std::ofstream outputFile(out_filename.c_str(), std::ofstream::trunc);
if (sourceFile.is_open())
{
std::cout << "Opened file: " + filename + " for decryption" << std::endl;
std::string line;
std::string::size_type lineLen;
long numLines = 0;
while (sourceFile.read((char*)&lineLen, sizeof(lineLen))) // This iterates over the whole file, once for each line
{
line.resize(lineLen);
if (!sourceFile.read(&line[0], lineLen))
break;
for (std::string::size_type i = 0; i < lineLen; ++i) // Looping through all characters in each line
{
char focusByte = line[i] ^ encryptionKey;
std::cout << " focusByte: " << focusByte << std::endl;
line[i] = focusByte;
}
outputFile << line << std::endl;
++numLines;
}
std::cout << "eof" << std::endl;
}
}
int main(int argument_count, char* argument_list[])
{
std::system("color a");
std::string filename;
if (argument_count < 2)
{
std::cout << "Enter a file to process: " << std::flush;
std::getline(std::cin, filename);
}
else
{
filename = argument_list[1];
}
if (filename.empty())
{
std::cout << "You didn't supply a filename" << std::endl;
return EXIT_FAILURE;
}
std::cout << "Target file: " << filename << std::endl;
std::cout << "Press e to encrypt the file" << std::endl;
std::cout << "Press d to decrypt the file" << std::endl;
char choice;
while (true)
{
std::cout << "> " << std::flush;
std::cin >> choice;
if (choice == 'e')
{
Encrypt(123, filename);
break;
}
else if (choice == 'd')
{
Decrypt(123, filename);
break;
}
else
{
std::cout << "please choose option e or d for encryption or decryption, respectively" << std::endl;
}
}
std::cout << std::endl << "Paused, press Enter to continue" << std::flush;
std::system("pause");
return EXIT_SUCCESS;
}
ASCII value 26 is EOF on some operating systems.
You should probably treat your encrypted file as a byte stream rather than a text file for reading and writing. That means either using read() and write() functions of the IOStream or at the very least opening the files in binary mode.
If you're just enciphering your text instead of encrypting, maybe choose a different cipher (eg. ROT13) that is closed on the set of printable ASCII or UTF-8 characters.
I compiled your code in Linux (minus all the Windows stuff)...
I get this when encrypting your sentence with your code:
/[[[[[
[[[ [[[U
It also decrypts back to the original sentence. Without the goofy characters, it is the same as your output so your actual issue seems related to the encoding of the file and the program you are using to view the results. Stephan is correct in saying you should be reading/writing bytes instead of text. This can cause all sorts of issues with the characters you create. For example, line feeds and carriage returns since you are using getline().
Edit: Strange. After editing this answer, all the odd characters disappeared. Here is a screenshot:
I am writing a C++ code to calculate the code coverage and I want to used the OpenMP to help enhance my code by minimizing the overall run time by making the functions work in parallel so I can get less run time.
Can someone please tell me how and where to use the OpenMP?
int _tmain(int argc, _TCHAR* argv[])
{
std::clock_t start;
start = std::clock();
char inputFilename[] = "Test-Case-3.cs"; // Test Case File
char outputFilename[] = "Result.txt"; // Result File
int totalNumberOfLines = 0;
int numberOfBranches = 0;
int statementsCovered = 0;
float statementCoveragePercentage = 0;
double overallRuntime = 0;
ifstream inFile; // object for reading from a file
ofstream outFile; // object for writing to a file
inFile.open(inputFilename, ios::in);
if (!inFile) {
cerr << "Can't open input file " << inputFilename << endl;
exit(1);
}
totalNumberOfLines = NoOfLines(inFile);
inFile.clear(); // reset
inFile.seekg(0, ios::beg);
numberOfBranches = NoOfBranches(inFile);
inFile.close();
statementsCovered = totalNumberOfLines - numberOfBranches;
statementCoveragePercentage = (float)statementsCovered * 100/ totalNumberOfLines;
outFile.open(outputFilename, ios::out);
if (!outFile) {
cerr << "Can't open output file " << outputFilename << endl;
exit(1);
}
outFile << "Total Number of Lines" << " : " << totalNumberOfLines << endl;
outFile << "Number of Branches" << " : " << numberOfBranches << endl;
outFile << "Statements Covered" << " : " << statementsCovered << endl;
outFile << "Statement Coverage Percentage" << " : " << statementCoveragePercentage <<"%"<< endl;
overallRuntime = (std::clock() - start) / (double)CLOCKS_PER_SEC;
outFile << "Overall Runtime" << " : " << overallRuntime << " Seconds"<< endl;
outFile.close();
}
i want to minimize the time taken to count the number of branches by allowing multiple threads to work in parallel to calculate the number faster? how can i edit the code so that i can use the open mp and here you can find my functions:bool is_only_ascii_whitespace(const std::string& str)
{
auto it = str.begin();
do {
if (it == str.end()) return true;
} while (*it >= 0 && *it <= 0x7f && std::isspace(*(it++)));
// one of these conditions will be optimized away by the compiler,
// which one depends on whether char is signed or not
return false;
}
// Function 1
int NoOfLines(ifstream& inFile)
{
//char line[1000];
string line;
int lines = 0;
while (!inFile.eof()) {
getline(inFile, line);
//cout << line << endl;
if ((line.find("//") == std::string::npos)) // Remove Comments
{
if (!is_only_ascii_whitespace(line)) // Remove Blank
{
lines++;
}
}
//cout << line << "~" <<endl;
}
return lines;
}
// Function 2
int NoOfBranches(ifstream& inFile)
{
//char line[1000];
string line;
int branches = 0;
while (!inFile.eof()) {
getline(inFile, line);
if ((line.find("if") != std::string::npos) || (line.find("else") != std::string::npos))
{
branches++;
}
}
return branches;
}
Let me start off by stating that I am a beginner in C++. Anyways, the FASTA format goes as follows:
Any line starting with a '>' indicates the name/id of the gene sequence right below it. There is a gene sequence right below the id. This gene sequence can be 1 or multiple lines.
So... what I want to do is print: id << " : " << gene_sequence << endl;
Here is my code:
#include <iostream>
#include <fstream>
int main(int argc, char **argv) {
if (argc < 2) {
std::cerr << " Wrong format: " << argv[0] << " [infile] " << std::endl;
return -1;
}
std::ifstream input(argv[1]);
if (!input.good()) {
std::cerr << "Error opening: " << argv[1] << " . You have failed." << std::endl;
return -1;
}
std::string line, id, DNA_sequence;
while (std::getline(input, line).good()) {
if (line[0] == '>') {
id = line.substr(1);
std::cout << id << " : " << DNA_sequence << std::endl;
DNA_sequence.clear();
}
else if (line[0] != '>'){
DNA_sequence += line;
}
}
}
For the second argument inputted into the command line, here is the content of my file:
>DNA_1
GATTACA
>DNA_2
TAGACCA
TAGACCA
>DNA_3
ATAC
>DNA_4
AT
Please copy and paste into text file.
After this has been done, and the code has been executed, I want to point out the problem. The code skips inputting the sequence of DNA_1 into its correct respective place, and instead placing DNA_1 's sequence into DNA_2. The results get pushed forward 1 as a result. Any assistance or tips would be greatly appreciated?
As I've said before, I am new to C++. And the semantics are quite hard to learn compared to Python.
I see a few problems with your code.
First you loop on std::ifstream::good() which doesn't work because it won't allow for End Of File (which happens even after a good read).
Then you access line[0] without checking if the line is empty which could cause a seg-fault.
Next you output the "previous line" before you have even collected it.
Finally you don't output the final line because the loop terminates when it doesn't find another >.
I added comments to my corrections to your code:
#include <iostream>
#include <fstream>
int main(int argc, char **argv) {
if (argc < 2) {
std::cerr << " Wrong format: " << argv[0] << " [infile] " << std::endl;
return -1;
}
std::ifstream input(argv[1]);
if (!input.good()) {
std::cerr << "Error opening: " << argv[1] << " . You have failed." << std::endl;
return -1;
}
std::string line, id, DNA_sequence;
// Don't loop on good(), it doesn't allow for EOF!!
// while (std::getline(input, line).good()) {
while (std::getline(input, line)) {
// line may be empty so you *must* ignore blank lines
// or you have a crash waiting to happen with line[0]
if(line.empty())
continue;
if (line[0] == '>') {
// output previous line before overwriting id
// but ONLY if id actually contains something
if(!id.empty())
std::cout << id << " : " << DNA_sequence << std::endl;
id = line.substr(1);
DNA_sequence.clear();
}
else {// if (line[0] != '>'){ // not needed because implicit
DNA_sequence += line;
}
}
// output final entry
// but ONLY if id actually contains something
if(!id.empty())
std::cout << id << " : " << DNA_sequence << std::endl;
}
Output:
DNA_1 : GATTACA
DNA_2 : TAGACCATAGACCA
DNA_3 : ATAC
DNA_4 : AT
You're storing the new id before printing the old one:
id = line.substr(1);
std::cout << id << " : " << DNA_sequence << std::endl;
Swap the lines around for proper order. You probably also want to check if you have any id already present to skip the first entry.
working implementation is here
https://rosettacode.org/wiki/FASTA_format#C.2B.2B
only corrected
while( std::getline( input, line ).good() ){
to
while( std::getline( input, line ) ){
Code
#include <iostream>
#include <fstream>
int main( int argc, char **argv ){
if( argc <= 1 ){
std::cerr << "Usage: "<<argv[0]<<" [infile]" << std::endl;
return -1;
}
std::ifstream input(argv[1]);
if(!input.good()){
std::cerr << "Error opening '"<<argv[1]<<"'. Bailing out." << std::endl;
return -1;
}
std::string line, name, content;
while( std::getline( input, line ) ){
if( line.empty() || line[0] == '>' ){ // Identifier marker
if( !name.empty() ){ // Print out what we read from the last entry
std::cout << name << " : " << content << std::endl;
name.clear();
}
if( !line.empty() ){
name = line.substr(1);
}
content.clear();
} else if( !name.empty() ){
if( line.find(' ') != std::string::npos ){ // Invalid sequence--no spaces allowed
name.clear();
content.clear();
} else {
content += line;
}
}
}
if( !name.empty() ){ // Print out what we read from the last entry
std::cout << name << " : " << content << std::endl;
}
return 0;
}
input:
>Rosetta_Example_1
THERECANBENOSPACE
>Rosetta_Example_2
THERECANBESEVERAL
LINESBUTTHEYALLMUST
BECONCATENATED
output:
Rosetta_Example_1 : THERECANBENOSPACE
Rosetta_Example_2 : THERECANBESEVERALLINESBUTTHEYALLMUSTBECONCATENATED
I've been trying to trouble shoot this code for a couple of days now with no luck. I'm trying to read a CSV file (separated by a comma) that looks like this. I want to output the 100 spot (second row second column).
apple,party11,
0,0.1,
0.1,**100**,
//-Line 4 is empty-
My Code :
void Info() {
Input1 = CSVfile("File1.csv");
Input2 = CSVfile("File2.csv");
}
double CSVfile(string cvsfilein) {
ifstream file;
file.open(cvsfilein);
if (file.fail()) {
printf("----------Error no CSV File----------------");
return 0;
}
vector<vector<string>> csvfile;
double needvalue;
while (file) {
string filevalue1;
if (!getline(file, filevalue1)) {
cout << "failed heree1 " << endl;
return -2;
break;
}
** // Never get past here**
cout
<< "filevalue1 " << filevalue1 << endl;
istringstream iss(filevalue1);
vector<string> record;
while (iss) {
string filevalue2;
if (!getline(iss, filevalue2, ',')) {
if (filevalue2.empty())
continue;
cout << "failed heree2 " << endl;
return -2;
break;
}
record.push_back(filevalue2);
cout << "filevalue2 " << filevalue2 << endl;
}
csvfile.push_back(record);
needvalue = atof(record[3].c_str()); // Converts the string to number
cout << needvalue << endl; // just to check
return needvalue;
file.close();
}
}
I never seem to get passed the first if (!getline(file, filevalue1)). I've tried using if (filevalue1.empty()) continue; and it doesn't seem to continue the code.. just stops it.
The primary issue is the placement of file.close(), and secondary issues relate to various bits of unreachable code. This mildly modified version of your code seems to work, even managing not to crash on the empty line at the end of the file(s) — I used two identical data files.
#include <cstdlib>
#include <fstream>
#include <iostream>
#include <sstream>
#include <string>
#include <vector>
using namespace std;
double CSVfile(string cvsfilein);
void Info();
double Input1;
double Input2;
void Info() {
Input1 = CSVfile("File1.csv");
Input2 = CSVfile("File2.csv");
}
double CSVfile(string cvsfilein) {
ifstream file;
file.open(cvsfilein);
if (file.fail()) {
cerr << "----------Error no CSV File----------------\n";
return 0;
}
vector<vector<string>> csvfile;
while (file) {
string filevalue1;
if (!getline(file, filevalue1)) {
cerr << "failed heree1 " << endl;
return -2;
break;
}
cout << "filevalue1 " << filevalue1 << endl;
istringstream iss(filevalue1);
vector<string> record;
while (iss) {
string filevalue2;
if (!getline(iss, filevalue2, ',')) {
if (filevalue2.empty())
continue;
cerr << "failed heree2 " << endl;
return -2;
}
record.push_back(filevalue2);
cout << "filevalue2 " << filevalue2 << endl;
}
csvfile.push_back(record);
//double needvalue = atof(record[3].c_str()); // Converts the string to number
//cout << needvalue << endl; // just to check
//return needvalue;
//file.close();
}
file.close();
return 0;
}
int main()
{
Info();
return 0;
}
Sample output:
filevalue1 apple,party11,
filevalue2 apple
filevalue2 party11
filevalue1 0,0.1,
filevalue2 0
filevalue2 0.1
filevalue1 0.1,100,
filevalue2 0.1
filevalue2 100
filevalue1
failed heree1
filevalue1 apple,party11,
filevalue2 apple
filevalue2 party11
filevalue1 0,0.1,
filevalue2 0
filevalue2 0.1
filevalue1 0.1,100,
filevalue2 0.1
filevalue2 100
filevalue1
failed heree1
The needvalue computation crashes the program on the empty line (dereferencing a null pointer in strtod() called from within atof()). That's because there isn't a record[3] entry to convert to a string — not unreasonable.
It worked for me too (exactly until the conversion from string to double).
Firts of all getline returns an istream& so don't put it inside an if.
Now, If the "failed heree1" error isn't printed at all use try & catch.
Moreover, check the error bits:
try {
getline(file, filevalue1);
} catch(ifstream::failure e) {
cerr << "Exception happened: " << e.what() << endl
<< "Error bits are: "
<< "\nfailbit: " << file.fail()
<< "\neofbit: " << file.eof()
<< "\nbadbit: " << file.bad() << endl;
}
eofbit - The end of the source of characters is reached during its operations.
failbit - The input obtained could not be interpreted as a valid textual representation of an object of this type. Notice that some eofbit cases will also set failbit.
badbit - An error other than the above happened.
it failbit is on i would put my money on the csv-file's encoding.
source: http://www.cplusplus.com/reference/string/string/getline/