I'm working on a project and I need to select a different .txt every time based on the input.
This is what I have:
#include <iostream>
#include <cstdlib>
#include <time.h>
#include <fstream>
#include <string>
#include <stdio.h>
using namespace std;
int main()
{
string hp, att, def, vel, spec;
string answer, monster;
do
{
cout << "Which Monster?: ";
cin >> monster;
cout << endl;
ifstream selection;
selection.open(monster+".txt");
selection.close();
cout << endl << "Again? ";
cin >> answer;
}
while (answer == "y");
cout << "Hello world!" << endl;
return 0;
}
I have to get the monster string and search the .txt with the same name.
If I type "Troll" it will search for the Troll.txt
Is there a way?
This is the error I get:
F:\GdR\Campagna 1\CalcoloStats\main.cpp|22|error: no matching function for call to 'std::basic_ifstream::open(std::__cxx11::basic_string)'|
Given that monster is a std::string, this expression:
monster + ".txt"
is also a std::string.
Since C++11, you can use this as an argument to ifstream's open function just fine. However, until then, you are stuck with a limitation of ifstream which is that it can only take a C-style string.
Fortunately, you can get a C-style string from a std::string using the c_str() member function.
So, either:
selection.open((monster + "txt").c_str());
Or get a modern compiler / switch out of legacy mode.
Thanks Lightness Races in Orbit, solved with C++11 Compiler flag
Related
In my program it should be an option to ask a user for input, and then save input string into the file. My problem is, - when I put cin in any of it forms, inside Switch, program will stuck circling indefinitely, right after i press enter after finish typing new text. What could cause the problem?
#include <iostream>
#include <fstream>
#include <iterator>
#include <string.h>
#include <time.h>
#include <stdlib.h>
#include <algorithm>
#include <chrono>
#include <random>
#include <vector>
using namespace std;
void changePlainText()
{
ofstream nFile("plaintext.txt");
string newText;
cout << "Enter new plain text" << endl;
getline(cin, newText);
nFile << newText;
nFile.close();
}
int main()
{
int uInput = 0;
do
{
printf("2.Change content of the plain text file: \n");
cin >> uInput;
switch (uInput)
{
case 1:
break;
case 2:
changePlainText();
break;
}
} while (uInput != 5);
cout << "Closing program" << endl;
system("pause");
}
After I type something in console and press enter, the program enters never ending circle. It still stuck even if I just write simple cin >> i, in switch case.
Take a look at this question. I debugged your code and I experienced that exact behavior. The accepted answer explains quite well what's happening and also provides a solution.
I tried with boost, I changed
cin >> uInput;
to
string inputString; // so you know what inputString is
getline(cin, inputString);
uInput = boost::lexical_cast<int>(line);
and it's working fine now.
#include <string>
std::string input;
std::cin >> input;
The user wants to enter "Hello World". But cin fails at the space between the two words. How can I make cin take in the whole of Hello World?
I'm actually doing this with structs and cin.getline doesn't seem to work. Here's my code:
struct cd
{
std::string CDTitle[50];
std::string Artist[50];
int number_of_songs[50];
};
std::cin.getline(library.number_of_songs[libNumber], 250);
This yields an error. Any ideas?
It doesn't "fail"; it just stops reading. It sees a lexical token as a "string".
Use std::getline:
#include <string>
#include <iostream>
int main()
{
std::string name, title;
std::cout << "Enter your name: ";
std::getline(std::cin, name);
std::cout << "Enter your favourite movie: ";
std::getline(std::cin, title);
std::cout << name << "'s favourite movie is " << title;
}
Note that this is not the same as std::istream::getline, which works with C-style char buffers rather than std::strings.
Update
Your edited question bears little resemblance to the original.
You were trying to getline into an int, not a string or character buffer. The formatting operations of streams only work with operator<< and operator>>. Either use one of them (and tweak accordingly for multi-word input), or use getline and lexically convert to int after-the-fact.
You have to use cin.getline():
char input[100];
cin.getline(input,sizeof(input));
The Standard Library provides an input function called ws, which consumes whitespace from an input stream. You can use it like this:
std::string s;
std::getline(std::cin >> std::ws, s);
Use :
getline(cin, input);
the function can be found in
#include <string>
You want to use the .getline function in cin.
#include <iostream>
using namespace std;
int main () {
char name[256], title[256];
cout << "Enter your name: ";
cin.getline (name,256);
cout << "Enter your favourite movie: ";
cin.getline (title,256);
cout << name << "'s favourite movie is " << title;
return 0;
}
Took the example from here. Check it out for more info and examples.
How do I read a string from input?
You can read a single, whitespace terminated word with std::cin like this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a word:\n";
string s;
cin>>s;
cout << "You entered " << s << '\n';
}
Note that there is no explicit memory management and no fixed-sized buffer that you could possibly overflow.
If you really need a whole line (and not just a single word) you can do this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a line:\n";
string s;
getline(cin,s);
cout << "You entered " << s << '\n';
}
THE C WAY
You can use gets function found in cstdio(stdio.h in c):
#include<cstdio>
int main(){
char name[256];
gets(name); // for input
puts(name);// for printing
}
THE C++ WAY
gets is removed in c++11.
[Recommended]:You can use getline(cin,name) which is in string.h
or cin.getline(name,256) which is in iostream itself.
#include<iostream>
#include<string>
using namespace std;
int main(){
char name1[256];
string name2;
cin.getline(name1,256); // for input
getline(cin,name2); // for input
cout<<name1<<"\n"<<name2;// for printing
}
I rather use the following method to get the input:
#include <iostream>
#include <string>
using namespace std;
int main(void) {
string name;
cout << "Hello, Input your name please: ";
getline(cin, name);
return 0;
}
It's actually super easy to use rather than defining the total length of array for a string which contains a space character.
#include <string>
std::string input;
std::cin >> input;
The user wants to enter "Hello World". But cin fails at the space between the two words. How can I make cin take in the whole of Hello World?
I'm actually doing this with structs and cin.getline doesn't seem to work. Here's my code:
struct cd
{
std::string CDTitle[50];
std::string Artist[50];
int number_of_songs[50];
};
std::cin.getline(library.number_of_songs[libNumber], 250);
This yields an error. Any ideas?
It doesn't "fail"; it just stops reading. It sees a lexical token as a "string".
Use std::getline:
#include <string>
#include <iostream>
int main()
{
std::string name, title;
std::cout << "Enter your name: ";
std::getline(std::cin, name);
std::cout << "Enter your favourite movie: ";
std::getline(std::cin, title);
std::cout << name << "'s favourite movie is " << title;
}
Note that this is not the same as std::istream::getline, which works with C-style char buffers rather than std::strings.
Update
Your edited question bears little resemblance to the original.
You were trying to getline into an int, not a string or character buffer. The formatting operations of streams only work with operator<< and operator>>. Either use one of them (and tweak accordingly for multi-word input), or use getline and lexically convert to int after-the-fact.
You have to use cin.getline():
char input[100];
cin.getline(input,sizeof(input));
The Standard Library provides an input function called ws, which consumes whitespace from an input stream. You can use it like this:
std::string s;
std::getline(std::cin >> std::ws, s);
Use :
getline(cin, input);
the function can be found in
#include <string>
You want to use the .getline function in cin.
#include <iostream>
using namespace std;
int main () {
char name[256], title[256];
cout << "Enter your name: ";
cin.getline (name,256);
cout << "Enter your favourite movie: ";
cin.getline (title,256);
cout << name << "'s favourite movie is " << title;
return 0;
}
Took the example from here. Check it out for more info and examples.
How do I read a string from input?
You can read a single, whitespace terminated word with std::cin like this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a word:\n";
string s;
cin>>s;
cout << "You entered " << s << '\n';
}
Note that there is no explicit memory management and no fixed-sized buffer that you could possibly overflow.
If you really need a whole line (and not just a single word) you can do this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a line:\n";
string s;
getline(cin,s);
cout << "You entered " << s << '\n';
}
THE C WAY
You can use gets function found in cstdio(stdio.h in c):
#include<cstdio>
int main(){
char name[256];
gets(name); // for input
puts(name);// for printing
}
THE C++ WAY
gets is removed in c++11.
[Recommended]:You can use getline(cin,name) which is in string.h
or cin.getline(name,256) which is in iostream itself.
#include<iostream>
#include<string>
using namespace std;
int main(){
char name1[256];
string name2;
cin.getline(name1,256); // for input
getline(cin,name2); // for input
cout<<name1<<"\n"<<name2;// for printing
}
I rather use the following method to get the input:
#include <iostream>
#include <string>
using namespace std;
int main(void) {
string name;
cout << "Hello, Input your name please: ";
getline(cin, name);
return 0;
}
It's actually super easy to use rather than defining the total length of array for a string which contains a space character.
#include <string>
std::string input;
std::cin >> input;
The user wants to enter "Hello World". But cin fails at the space between the two words. How can I make cin take in the whole of Hello World?
I'm actually doing this with structs and cin.getline doesn't seem to work. Here's my code:
struct cd
{
std::string CDTitle[50];
std::string Artist[50];
int number_of_songs[50];
};
std::cin.getline(library.number_of_songs[libNumber], 250);
This yields an error. Any ideas?
It doesn't "fail"; it just stops reading. It sees a lexical token as a "string".
Use std::getline:
#include <string>
#include <iostream>
int main()
{
std::string name, title;
std::cout << "Enter your name: ";
std::getline(std::cin, name);
std::cout << "Enter your favourite movie: ";
std::getline(std::cin, title);
std::cout << name << "'s favourite movie is " << title;
}
Note that this is not the same as std::istream::getline, which works with C-style char buffers rather than std::strings.
Update
Your edited question bears little resemblance to the original.
You were trying to getline into an int, not a string or character buffer. The formatting operations of streams only work with operator<< and operator>>. Either use one of them (and tweak accordingly for multi-word input), or use getline and lexically convert to int after-the-fact.
You have to use cin.getline():
char input[100];
cin.getline(input,sizeof(input));
The Standard Library provides an input function called ws, which consumes whitespace from an input stream. You can use it like this:
std::string s;
std::getline(std::cin >> std::ws, s);
Use :
getline(cin, input);
the function can be found in
#include <string>
You want to use the .getline function in cin.
#include <iostream>
using namespace std;
int main () {
char name[256], title[256];
cout << "Enter your name: ";
cin.getline (name,256);
cout << "Enter your favourite movie: ";
cin.getline (title,256);
cout << name << "'s favourite movie is " << title;
return 0;
}
Took the example from here. Check it out for more info and examples.
How do I read a string from input?
You can read a single, whitespace terminated word with std::cin like this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a word:\n";
string s;
cin>>s;
cout << "You entered " << s << '\n';
}
Note that there is no explicit memory management and no fixed-sized buffer that you could possibly overflow.
If you really need a whole line (and not just a single word) you can do this:
#include<iostream>
#include<string>
using namespace std;
int main()
{
cout << "Please enter a line:\n";
string s;
getline(cin,s);
cout << "You entered " << s << '\n';
}
THE C WAY
You can use gets function found in cstdio(stdio.h in c):
#include<cstdio>
int main(){
char name[256];
gets(name); // for input
puts(name);// for printing
}
THE C++ WAY
gets is removed in c++11.
[Recommended]:You can use getline(cin,name) which is in string.h
or cin.getline(name,256) which is in iostream itself.
#include<iostream>
#include<string>
using namespace std;
int main(){
char name1[256];
string name2;
cin.getline(name1,256); // for input
getline(cin,name2); // for input
cout<<name1<<"\n"<<name2;// for printing
}
I rather use the following method to get the input:
#include <iostream>
#include <string>
using namespace std;
int main(void) {
string name;
cout << "Hello, Input your name please: ";
getline(cin, name);
return 0;
}
It's actually super easy to use rather than defining the total length of array for a string which contains a space character.
In his answer, specifically in the linked Ideone example, #Nawaz shows how you can change the buffer object of cout to write to something else. This made me think of utilizing that to prepare input from cin, by filling its streambuf:
#include <iostream>
#include <sstream>
using namespace std;
int main(){
streambuf *coutbuf = cout.rdbuf(cin.rdbuf());
cout << "this goes to the input stream" << endl;
string s;
cin >> s;
cout.rdbuf(coutbuf);
cout << "after cour.rdbuf : " << s;
return 0;
}
But this doesn't quite work as expected, or in other words, it fails. :| cin still expects user input, instead of reading from the provided streambuf. Is there a way to make this work?
#include <iostream>
#include <sstream>
int main()
{
std::stringstream s("32 7.4");
std::cin.rdbuf(s.rdbuf());
int i;
double d;
if (std::cin >> i >> d)
std::cout << i << ' ' << d << '\n';
}
Disregard that question, while further investigating it, I made it work. What I did was actually the other way around than planned; I provided cin a streambuf to read from instead of filling its own.
#include <iostream>
#include <sstream>
#include <string>
using namespace std;
int main(){
stringstream ss;
ss << "Here be prepared input for cin";
streambuf* cin_buf = cin.rdbuf(ss.rdbuf());
string s;
while(cin >> s){
cout << s << " ";
}
cin.rdbuf(cin_buf);
}
Though it would still be nice to see if it's possible to provide prepared input without having to change the cin streambuf directly, aka writing to its buffer directly instead of having it read from a different one.