CODEWITHSUNDEEP
c++visual-c++-2010-express
Ram Sidharth
Ram Sidharth

Reputation: 183

For Loops in C++ - Variables not being incremented properly

I have been trying to write some code that asks the user for several debit entries for an accounting program. If the user gives 5 as the answer, the program should ask him the debit entry's name and amount 5 times before continuing on to the next line of code. So, I used for loops to solve this problem and it seems something strange is happening.

This is the format in which the code should run when being compiled and executed:

How many debit entries do you wish to make?: 2
1. Debit Entry Name: example1
1. Debit Amount: 123
2. Debit Entry Name: example2
2. Debit Amount: 456


continue on to next line of code

Here's the code I've written in C++ for this part of the accounting program:

#include <iostream>
#include <string>
using namespace std;

int main()
{
   cout << "How many debit entries do you wish to make?: ";
   int entries;
   cin >> entries;
   string debitNames[50];
   float debitAmounts[50];
   int offset = 0;
   int number = 1;
   for (offset = 0; offset < entries; offset++)
   {
      cout << number << ". Debit Entry Name: ";
      cin >> debitNames[offset];
      cout << number << ". Debit Amount: ";
      cin >> debitAmounts[offset];
      for (number = 1; number <= entries; number++)
      {
      }
   }
   char response;
   cin >> response;
   return 0;
}



The outcome is extremely strange, here is what happens when I compile and run it:

How many debit entries to do you wish to make?: 5
1. Debit Entry Name: example1
1. Debit Amount: 123
6. Debit Entry Name: example2
6. Debit Amount : 123
6. Debit Entry Name: example3
6. Debit Amount: 123
6. Debit Entry Name: example4
6. Debit Amount: 123
6. Debit Entry Name: example5
6. Debit Amount: 123

continue on to next line of code

The program, after listing the number as 1, suddenly jumps off to 6 and remains there until all the 5 sets of questions have been asked. As you know by now I'm using the 'number' variable to simply tell the user that 'number' entries have been asked, as specified by the user his/herself. Try running this code in your compiler and see whether the same result appears. By the way, I use Visual C++ 20120 Express Edition, could this have anything do with the problem?

Thanks a lot.

Upvotes: 0

Views: 2337

Answers (6)

James Allan
James Allan

Reputation: 313

you want to add 1 to the number at the end of the loop. The simplest way to do this is to use:

    number++;

the for loop 

  for (number = 1; number <= entries; number++)   
  {   
  }

is completely unneccesary, when coding, always start with the simplest solution you can imagine and get more complex as you proceed.

Upvotes: 0

teodozjan
teodozjan

Reputation: 913

Why don't you? 

  number++;
  for (int number = 1; number <= entries; number++)
  {
  }

Also some more close to real life solution is to not to hold this separately. It is much more logical to create struct or class.

#include <iostream>
#include <list>
#include <time.h>
#include<string>
using namespace std;

struct Debt{

  string name;
  float owe;
};


int main()
{
cout << "How many debit entries do you wish to make?: ";
int entries;
cin >> entries;
list<Debt> debts;



for (int offset = 1; offset <= entries; offset++)
{
  Debt debt;

  cout << offset << ". Debit Entry Name: ";
  cin >> debt.name;

  cout << offset << ". Debit Amount: ";
  cin >> debt.owe;

  debts.push_back(debt);

  for (int number = 1; number <= entries; number++)
  {
  }
}
int i=0;
list<Debt>::iterator it;
for ( it=debts.begin() ; it != debts.end(); it++ )
  cout << "Debt seq " << ++i << " Name " << (*it).name << " debt is " << (*it).owe << endl;


char response;
cin >> response;
return 0;
}

Upvotes: 0

Aman Aggarwal
Aman Aggarwal

Reputation: 4005

Obviously the bug is in this part of code :

for (number = 1; number <= entries; number++)
      {
      }

You are using number to display debit entry number

And it is incremented in the above loop to enteries + 1

Upvotes: 1

Abrixas2
Abrixas2

Reputation: 3295

You output the number variable, which you incremented in your inner for loop to entries+1...

Upvotes: 0

Anders Marzi Tornblad
Anders Marzi Tornblad

Reputation: 19305

Well, before the loop, you set the number variable to 1.

Inside the loop, you set the number variable to (entries + 1) using this snippet:

for (number = 1; number <= entries; number++)
{
}

Why not simply do this?

cout << (offset + 1) << ". Debit Entry Name: ";

Upvotes: 1

Alan Stokes
Alan Stokes

Reputation: 18974

Your inner for loop will always leave number at entries+1:

  for (number = 1; number <= entries; number++)
  {
  }

Did you mean to use a different variable here, rather than re-use the existing number?

Upvotes: 1

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