#include <iostream>
int main()
{
int x{ 19 };
std::cout << "Hola!" << '\n';
std::cout << "Me llamo Kay\n";
std::cout << "And I am " << x << " years old\n";
std::cout << "Who are you?\n";
int y{};
std::cin >> y;
std::cout << "You are " << y << "?" << '\n';
return 0;
}
So i want the code to run a program that goes:
Hola!
Me llamo Kay
And I am 19 years old
Who are you?
[user enters whatever]
You are [user entered]?
But instead what I get is:
Hola!
Me llamo Kay
And I am 19 years old
Who are you?
[user enters whatever]
You are 0?
Edit: enter image description here
You declared y as an integer. This means y can only be used to contain a number. In your case, you want a to contain a std::string. This means any kind of text, like the text the user has entered. So simply change int y{} into std::string y;. And don't forget you can only declare a variable once in c++, so you'll have to remove one of the declarations for y.
Related
I have set the size of the character array to 2 bytes. But it can hold more than 2 bytes. how is it possible?
#include<iostream>
int main() {
char a[2];
std::cout << "enter the name" << std::endl;
std::cin >> a;
std::cout << "the name is " << a << std::endl;
system("pause");
return 0;
}
I am expecting some other output
but the output is .....
enter the name
Sami
the name is Sami
What happens is that you are effectively writing past the end of the allocated memory.
C++ doesn't check that the input provided fits intothe variable a so you are actually writing out of the bounds of the memory allocated to your program, resulting in Undefined Behaviour.
Your program seems to work, but you have actually no guarantees that it will behave as you wish.
Don't use a fixed size array of char, but use std::string instead.
Here is a fixed code example.
#include<iostream>
#include<string>
int main() {
std::string a;
std::cout << "enter the name" << std::endl;
std::getline(std::cin, a);
std::cout << "the name is " << a << std::endl;
system("pause");
return 0;
}
NOTE: I am new to C++ and may do things that are bad practice and if you see that please tell me so I can fix that and please don't be mean. I have only started coding 1-2 months ago. And I am still learning. Please be open to the fact I may not know everything.
This is a console text-based game. It works great! Although, I am creating a feature in it to allow the user to drag and drop any amount of other databases on it to allow database transfers. Although this works fine the problem is that I have a little process it will do to try and make sure none of the info in the databases is the same by placing a number to them,
Example there will be 2 profiles 1 in each file. They are both named main. Then the user drags the second database onto the game and it loads that database into the original one. But now becuase there are 2 SIMILAR profile names it won't be able to differentiate which is which. So then it goes through a little function which scans the database and places a number in front of the copies. Starting at 5 and working its way up. Although this would seem to work and not be that hard to actually do I have hit a problem and I do not know what is wrong. I do know however it is something with how it scans for duplicates. Please help.
I have tried for like a whole day trying different methods or re-writing the code. Google has not revealed a lot to me.
I am using the following libraries in my code. (Some might not be used in the example but tbh I don't remember which is directly used in THIS function).
#include <iostream>
#include <iterator>
#include <cstring>
#include <cmath>
#include <cassert>
#include <string>
#include <cstdlib>
#include <ctime>
#include <algorithm>
#include <utility>
#include <vector>
#include <array>
#include <functional>
#include <fstream>
Here is the scanning function to make sure there are no duplicate profiles.
Let me explain what happens.
I make a ton of variables which are used in the database. As you can see inside of the database it has a certain order.
Using file stream I access the database. (I have a function which will combine all the databases the user dragged in and the current profiles and data which works just fine).
The pattern in the database looks something like this.
profile_name user_name 100 3 0 0 0 0 knight 1 100 0 0
profile name health etc
If you look at the variables you will see the technical order.
void scanCopy()
{
std::string profile{ "John's_Profile" };
std::string name{ "John_Doe" };
int health{ 0 };
int damage{ 0 };
int gold{ 0 };
int exp{ 0 };
int level{ 0 };
int score{ 0 };
std::string CLASS{ "null" };
int dungeon{ 0 };
int maxHealth{ 0 };
int lives{ 0 };
int kills{ 0 };
std::ifstream in("data/database.txt");
std::vector <std::string> profiles;
int sizeOfVector{ 0 };
while (in >> profile >> name >> health >> damage >> gold >> exp >> level >> score >> CLASS >> dungeon >> maxHealth >> lives >> kills)
{
profiles.resize(sizeOfVector += 1);
profiles.at(sizeOfVector - 1) = { profile };
std::cout << profiles.at(sizeOfVector - 1) << "\n\n";
}
in.close();
for (int loop{ 0 }; loop < sizeOfVector; ++loop)
{
int compare{ loop };
for (int index{ loop }; index < sizeOfVector; ++index)
{
if (compare == index)//meaning they are like at profiles(1)and (1)
continue;
if (profiles.at(compare) == profiles.at(index))
{
std::ofstream out("data/~database.txt", std::ios::app);
in.open("data/database.txt");
int nameIndex{ 5 };
while (in >> profile >> name >> health >> damage >> gold >> exp >> level >> score >> CLASS >> dungeon >> maxHealth >> lives >> kills)
{
if (profile == profiles.at(index))
{
out << profile << nameIndex << " " << name << " " << health << " " << damage << " " << gold << " " << exp << " " << level << " " << score << " " << CLASS << " " << dungeon << " " << maxHealth << " " << lives << " " << kills << " " << std::endl; //Notice at the start profile is put into the database with an extra variable nameIndex to make its name now unique.
++nameIndex;
}
else
{
out << profile << " " << name << " " << health << " " << damage << " " << gold << " " << exp << " " << level << " " << score << " " << CLASS << " " << dungeon << " " << maxHealth << " " << lives << " " << kills << " " << std::endl;
}
}
}
}
}
in.close();
remove("data/database.txt");
in.open("data/~database.txt");
std::ofstream out("data/database.txt", std::ios::app);
//A buffer to copy everything inside a file to a string.
std::string upData((std::istreambuf_iterator<char>(in)),
(std::istreambuf_iterator<char>()));
/////
if (out)
out << upData; //putting everything in the tmp file to the file named database.txt
out.close();
in.close();
remove("data/~database.txt");
in.close();
out.close();
}
The problem is that it does not do its job. It will put numbers by anything. Besides that, it will also seem to overflow or something. What it does is after you already dragged something in, it pretends to work. Then any more input from dragging it does not get scanned. Thing is that everything is copied from the files the user drags from the database to a tmp file. Then the database is deleted and the temp file is renamed to database.txt. The problem is that this whole scan function seems to not be working right and I don't see the problem in it. Does anyone know a good way to do something like this or what the problem is? Thanks!
We really do not need the backstory that this is a game, that users can do XYZ and so on. Please construct a minimal example, as in minimal reproducible example. Often by constructing those, you yourself discover the problem. – Fureeish
Thank you Fureeish. I have found the problem. I was sending the function too many times which wiped the file or it did not scan it all the way. It is hard to explain the real thing I did because it was easy but I can't explain it well.
ALL IN ALL. I examined and found the bug, I was sending it to this function I posted up there too many times. or too little times.
This question already has answers here:
Two 'main' functions in C/C++
(13 answers)
Closed 3 years ago.
I know it is duplicated... I didn't understand any of the other threads. Literally just started to learn programming. Currently trying to learn C++ as my first language. Ran into this error, I did google it but I didn't really know what they were talking about. I looked at both of my "int main" things and they are exactly the same. No errors. I guess formatted wrong. Here is the code. I'm currently playing around with the std::count and variables, along with std:cin
#include <iostream>
int main()
{
std::cout << "Hello, how are you doing? I suppose you are only here to read this. Oh well.";
return 0;
}
int main()
{
std::cout << "Please feed me a number: " << "It can be any number."; // Asking human to enter a number.
int x{ }; // get number from keyboard and store it in value x
std::cin >> x; // recieved number and is now entering console
std::cout << "Thank you for feeding me " << x << '\n';
return 0;
}
A C++ program need only one main() function. This latter is called at program startup. Your code should look like this :
#include <iostream>
int main()
{
std::cout << "Hello, how are you doing? I suppose you are only here to read this. Oh well." << std::endl;
std::cout << "Please feed me a number: " << " It can be any number." << std::endl; // Asking human to enter a number.
int x{ }; // get number from keyboard and store it in value x
std::cin >> x; // recieved number and is now entering console
std::cout << "Thank you for feeding me " << x << std::endl;
return 0;
}
Here a link for more reading about the main() function.
I was just reviewing my C++. I tried to do this:
#include <iostream>
using std::cout;
using std::endl;
void printStuff(int x);
int main() {
printStuff(10);
return 0;
}
void printStuff(int x) {
cout << "My favorite number is " + x << endl;
}
The problem happens in the printStuff function. When I run it, the first 10 characters from "My favorite number is ", is omitted from the output. The output is "e number is ". The number does not even show up.
The way to fix this is to do
void printStuff(int x) {
cout << "My favorite number is " << x << endl;
}
I am wondering what the computer/compiler is doing behind the scenes.
The + overloaded operator in this case is not concatenating any string since x is an integer. The output is moved by rvalue times in this case. So the first 10 characters are not printed. Check this reference.
if you will write
cout << "My favorite number is " + std::to_string(x) << endl;
it will work
It's simple pointer arithmetic. The string literal is an array or chars and will be presented as a pointer. You add 10 to the pointer telling you want to output starting from the 11th character.
There is no + operator that would convert a number into a string and concatenate it to a char array.
adding or incrementing a string doesn't increment the value it contains but it's address:
it's not problem of msvc 2015 or cout but instead it's moving in memory back/forward:
to prove to you that cout is innocent:
#include <iostream>
using std::cout;
using std::endl;
int main()
{
char* str = "My favorite number is ";
int a = 10;
for(int i(0); i < strlen(str); i++)
std::cout << str + i << std::endl;
char* ptrTxt = "Hello";
while(strlen(ptrTxt++))
std::cout << ptrTxt << std::endl;
// proving that cout is innocent:
char* str2 = str + 10; // copying from element 10 to the end of str to stre. like strncpy()
std::cout << str2 << std::endl; // cout prints what is exactly in str2
return 0;
}
I recently started programming in c++ and I've bumped into a small problem. If I want my output to be structured (let's say that every line starts with a name and then a number) in a way that the names are written normally to the screen (every first letter of every name starts at the beginning of each new line) and I want the numbers that follow to be lined up in a column, how would I do this? I want the programs output to look like this:
Gary 0
LongName 0
VerylongName 0
I want my program to print something in the way above, but with different lengths of names (and the '0' in this case, lined up in a column).
Try the following: if you know the maximum length of all the names you intend to print (e.g. 20), then use the C++ i/o manipulators to set the width of the output (and left-justification). This will force the output to take up max characters.
Code snippet:
#include <iostream>
#include <iomanip>
...
// for each entry
std::cout << std::setw(20) << std::left << "Gary" << 10 << "\n";
...
std::cout << std::flush;
Here's some more information...
I'm shooting in the dark here since you haven't really included much information... HOWEVER one way you can do this is to make sure that you create the columns with padding around the name - and not worry about the numbers. Formatted output is one case where C has an advantage over C++ (IMHO). In C++ you can also do this with something like this:
cout << setw(15) << name << number << "\n";
Bonus points if you figure out ahead of time the maximum length of the name you have and add, say, 4 to it.
Not in the C++ standard library, but still worth mentioning: boost::format. It will let you write printf-like format strings while still being type-safe.
Example:
#include <boost/format.hpp>
#include <iostream>
#include <string>
struct PersonData
{
std::string name;
int age;
};
PersonData persons[] =
{
{"Gary", 1},
{"Whitney", 12},
{"Josephine ", 101}
};
int main(void)
{
for (auto person : persons)
{
std::cout << boost::format("%-20s %5i") % person.name % person.age << std::endl;
}
return 0;
}
Outputs:
Gary 1
Whitney 12
Josephine 101
struct X
{
const char *s;
int num;
} tab[] = {
{"Gary",1},
{"LongName",23},
{"VeryLongName",456}
};
int main(void)
{
for (int i = 0; i < sizeof(tab) / sizeof(struct X); i++ )
{
// C like - example width 20chars
//printf( "%-20s %5i\n", tab[i].s, tab[i].num );
// C++ like
std::cout << std::setw(20) << std::left << tab[i].s << std::setw(5) << std::right << tab[i].num << std::endl;
}
getchar();
return 0;
}