C++ help

• Skye wrote on 2012-09-21 02:52
  idk where else this would go, but I am to the point where I am mentally pulling my hair out and this seems like a logical place to post it.
  
  I have to make this program for one of my classes.
  [SPOILER="Spoiler"]You will write a program that can be use as a math tutor for students. The math tutor will keep track of the students progress by displaying the number of correct answers and the number of total problems attempted so far. The program will read these two numbers from a file called mathtutor.txt. You can create this file yourself. Just run you text editor and type a zero, hit enter, and type another zero. Then save the file as mathtutor.txt. I will show you how to read numbers from a file and write numbers to a file in class. Here's a preview:
  Here is an example program to read a number:
  
  [FONT="Courier New"]#include <iostream>
  #include <fstream>
  int main() {
  std::ifstream inf("mathtutor.txt");
  int number1;
  inf >> number1;
  std::cout << "Number is: " << number1 << std::endl;
  inf.close();
  return 0;
  }[/FONT]
  
  Here is an example program to write a number:
  
  [FONT="Courier New"]#include <iostream>
  #include <fstream>
  int main() {
  std::ofstream out("mathtutor.txt");
  int number1;
  std::cout << "what is your number: ";
  std::cin >> number1;
  out << number1;
  std::cout << "Done" << std::endl;
  out.close();
  return 0;
  }[/FONT]
  
  
  After displaying the number of correct answers and the total problems attempted so far, the math tutor program will generate two random numbers from 0 to 500 inclusive, and then ask the student to solve the addition problem. The program will prompt the student for the answer. Once the student has entered the answer, the program will check the answer, and, if the answer is correct, update the number of correct answers and the number of total problems solved. Lastly, the program will write these two values to the mathtutor.txt file and exit. Below is and example run of your program:
  
  [FONT="Courier New"]C:\mathtutor.exe
  
  Welcome to the Math Tutor!
  
  You have answered 0 problems correctly so far, out of a total of 0 problems.
  
  Here is your next problem:
  
  354
  + 18
  ----
  
  Your Answer: 372
  
  You are correct!
  
  Goodbye.
  
  C:\mathtutor.exe
  
  Welcome to the Math Tutor!
  
  You have answered 1 problems correctly so far, out of a total of 1 problems.
  
  Here is your next problem:
  
  16
  + 2
  ----
  
  Your Answer: 17
  
  Sorry, but that is the wrong answer.
  
  Goodbye.
  
  C:\mathtutor.exe
  
  Welcome to the Math Tutor!
  
  You have answered 1 problems correctly so far, out of a total of 2 problems.
  
  Here is your next problem:
  
  105
  + 182
  ----
  
  Your Answer: 287
  
  You are correct!
  
  Goodbye.[/FONT][/SPOILER]
  Now before i go any farther, I suck at this and hardly have any idea what I'm doing most of the time, so if you experienced folk look at this and go what the fuck, please forgive me. I went into this class thinking it was designed like another of mine, where anyone with any amount of knowledge can get into it.
  Anyway, this is my code.
  [SPOILER="Spoiler"][FONT="Courier New"]#include <iostream>
  #include <cstdlib>
  #include <fstream>
  int main() {
  std::ifstream inf("mathtutor.txt");
  std::ofstream out("mathtutor.txt");
  int correct;
  int total;
  int x = 0 + rand()% 500;
  int y = 0 + rand()% 500;
  inf >> correct;
  inf >> total;
  std::cout << "Welcome to the Math Tutor!" << std::endl;
  std::cout << "You have answered " << correct << " problems correctly so far, out of a
  total of " << total << " problems." << std::endl;
  inf.close();
  std::cout << x << "+" << y << "= " << std::endl;
  int answer;
  std::cout << "Your answer: ";
  std::cin >> answer;
  if (x + y == answer) {
  std::cout << "You are correct!" << std::endl;
  out << correct;
  std::cin << correct + 1 << std::endl;
  out.close();
  std::cout << "Goodbye." << std::endl;
  }
  if (x + y != answer) {
  std::cout << "Sorry, but that is the wrong answer." << std::endl;
  std::cout << "Goodbye." << std::endl;
  }
  else {
  out << total;
  std::cin << total + 1 << std::endl;
  out.close();
  }
  return 0;
  }[/FONT][/SPOILER]
  Whenever I try to compile it, I keep getting these errors for lines 23 and 33: "[FONT="Courier New"]no match for 'operator<<' in 'std::cin << (correct + 1)'[/FONT]" / "[FONT="Courier New"]no match for 'operator<<' in 'std::cin << (total + 1)'[/FONT]"
  
  Anyway please help because this is due tomorrow hahahahahahahahhahhahahhhahhhaha
  I'll keep trying to figure it out in the meantime ugh
  
  Also i thought this was really cute.
  

  [Image: http://puu.sh/176mQ]
• Okami wrote on 2012-09-21 02:58
  You wrote "std::cin << correct + 1 << std::endl;"
  
  Shouldn't it be "std::cin >> correct + 1 >> std::endl;?
  
  
  Ahh, your C++ looks so different than what I'm used too! /tries to help anyway
• Skye wrote on 2012-09-21 03:05
  ohmygod you're right i love you so much
  
  but now i'm getting "ambiguous overload" errors omfg i'm gonna kill myself this major was a terrible mistake
• Okami wrote on 2012-09-21 03:08
  Well, I'm going to take a guess and say it's because you can't take in an answer and just add 1 on to it like that. Try making another statement that does that separately and just have the lines say
  
  std::cin >> correct >> std::endl;
  And then another line with the adding + 1 on to the correct!
  Or something similar!
• Skye wrote on 2012-09-21 03:30
  yeah no, this just isn't working.
  i don't know what i'm doing
  
  I tried that out, but it didn't work, and i keep changing and rearranging things and the errors get worse and worse and then they get miraculously better than worse again. I guess I'll have to go see my professor tomorrow and ask him what the hell.
  
  Thanks for trying Okami, I really do appreciate it. +rep to you
  :kiss:
• Yoorah wrote on 2012-09-21 03:34
  The error has to do with function calls. Unfortunately, I have a killer headache and forgot most of my C++ stuff so I couldn't figure out the solution for you. D:
  
  PS. Girls doing C++ is pretty hot.
• Okami wrote on 2012-09-21 03:38
  No problem Skye! I would have typed out statements myself, but like I said your code is so much more different than what I'm used to having to write and look at. Good luck with figuring it out though! :)
  
  and LOL yoorah you silly goose
• Yoorah wrote on 2012-09-21 03:41
  It seems Okami's right, it's best done on a separate line. :o I got it to compile nao, but I dunno if it makes sense from a program logic point of view. /me tries to read it
• Yoorah wrote on 2012-09-21 04:03
  Some things that I suspected and confirmed... you can't have the inf and out objects on the same file instantiated at the same time. @_@ You're supposed to create one, use it, then close it ASAP. Normally, you'd write a separate function that would do it built in. Otherwise, you will read in junk.. even if you got your program to compile.
  
  Okay so... the first thing you need to know is how to properly read from and write to the file--in the format that the program demands. I messed around a bit and wrote an example program that reads the file in the format requested, displays the contents, then updates the file:
  
  [CODE]#include <iostream>
  #include <fstream>
  int main() {
  
  int number1;
  int number2;
  
  std::ifstream inf("mathtutor.txt");
  inf >> number1; //read the number on the first line
  inf >> number2; //read the number on the second line (ifstream utomatically switches the "reader" to the 2nd line)
  inf.close();
  
  std::cout << "Number is: " << number1 << " " << number2 << std::endl;
  
  number1 = number1 + 1; //let's update the numbers (in your case, it would be based on answers, total attempts)
  number2 = number2 + 1;
  
  std::ofstream out("mathtutor.txt");
  out << number1; //write updated number to file on line 1
  out << std::endl; //switch to line 2 in the file <-- important
  out << number2; //write updated number to the file on line 2
  out.close();
  
  std::cout << "Numbers were changed to: " << number1 << " " << number2 << std::endl;
  
  system("PAUSE");
  return 0;
  
  }
  [/CODE]
  
  I think that's the only tricky part here. The actual program logic for the math tester is pretty simple and you had most of it done correctly.
• Murasaki wrote on 2012-09-21 05:06
  Edit your posts when you add to them, y'all....
• Lolicon wrote on 2012-09-21 06:18
  Well the problem here is solved so its time to bounce.
  But ehh, that doesn't look like the C++ I did a while ago. Yeah I can read it, but the sexually transmitted diseases are everywhere.
• Yoorah wrote on 2012-09-21 14:13
  The way she was taught is actually more modern and correct. using namespace std is meant for compatibility with oldschool C++. You shouldn't use it in new programs.
  http://www.parashift.com/c++-faq-lite/using-namespace-std.html
• Lolicon wrote on 2012-09-22 17:52
  Dammit my teacher was old and groaty
• Skye wrote on 2012-09-28 02:02
  Would it be possible to get help again? :stress:
  
  This is the lab:
  

  [Image: http://puu.sh/19hz4]

  
  
  
  Here's my code (and I was actually feeling really good about it, but jesus i'm in error city)
  [CODE]#include <iostream>
  int main() {
  int filing;
  int income;
  int tax;
  char name[80];
  
  std::cout << "Tax Filing Categories: " << std::endl;
  std::cout << "1) Single " << std::endl;
  std::cout << "2) Married Filing Jointly" << std::endl;
  std::cout << "Enter Tax Filing Category: ";
  std::cin >> filing >> std::endl;
  
  if (filing == 1) {
  std::cout << "Enter First and Last Name: ";
  std::cin.ignore(80, '\n');
  std::cin.getline(name, 80);
  std::cout << "Enter 2011 Taxable Income: ";
  std::cin >> income >> std::endl;
  
  if (income > 60000) {
  double tax = income * .25;
  } else if (income > 40000) {
  double tax = income * .2;
  } else if (income > 10000) {
  double tax = income * .15;
  } else {
  double tax = income * .1;
  }
  
  std::cout << name << ": Your 2011 income tax is " << tax << " dollars." << std::endl;
  
  } else if (filing == 2) {
  std::cout << "Enter First and Last Name: ";
  std::cin.ignore(80, '\n');
  std::cin.getline(name, 80);
  std::cout << "Enter 2011 Taxable Income: ";
  std::cin >> income >> std::endl;
  
  if (income > 150000) {
  double tax = income * .25;
  } else if (income > 60000) {
  double tax = income * .2;
  } else if (income > 20000) {
  double tax = income * .15;
  } else {
  double tax = income * .1;
  }
  
  std::cout << name << ": Your 2011 income tax is " << tax << " dollars." << std::endl;
  
  } else {
  std::cout << "Invalid Filing Category";
  }
  return 0;
  }[/CODE]