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Having (mulitple) issues with my code

baked turkey (4)
Full disclosure: this is a homework project, so please do not give me complete answers on how to fix something, however please tell me whats wrong and hint at a fix please. Thank you all in advance for giving this a once over, I really appreciate it.
I am having major issues with vectors and getting the data to be displayed correctly. The top row of the table is supposed to be the monthly rate (starting at 3% increasing by 0.5% to 5.5%), and the row headings the years (starting at 15 ending at 30, increasing by 5year increments). However my program just displays the loan amount and nothing else. Any hints/help you could give would be greatly appreciated, because at the moment I am completely stuck.



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 using namespace std;
#include <cmath>
#include <iostream>
#include <iomanip>

int main(){
    
    //Heading and getting data from user
    cout << "Monthly Payment Calculator" << endl;
    cout << endl;
    
    //Variables and calculations
    double monthlyPayment;
    double monthlyRate;
    int months = 12;
    int loanAmount = 0.0;
    char answer = 'y';
    monthlyRate = 0.03;
   
    //Body Loop
    while (answer == 'y' || 'Y'){
        cout << "Please enter a valid loan amount (between 1000 - 500000): ";
        cin >> loanAmount;
        //Input Validation
        if (loanAmount < 1000 || loanAmount > 500000){
            cout << "Please enter a valid amount, between 1000 and 500000";
            cin >> loanAmount;
            cout << endl;
        }
        cout << "" << loanAmount;
        //Calculating results
        monthlyPayment = loanAmount * monthlyRate / (1 - 1 / pow((1 + monthlyRate), months));

        int grid [4][6] = {0};
        
        for (int iCol = 3; iCol < 6; iCol += 0.5){
            for (int iRow = 15; iRow < 33; iRow +=5 ){
                grid[iRow][iCol] = monthlyPayment;
            }
        }
        
        //displaying data
        cout << "      ";
        for( int iCol = 3; iCol < 6; iCol += 0.5){
            cout << setw(5) << iCol << "   ";
        }
        cout << endl;
        for(int iRow = 15; iRow < 33; iRow +=5 ){
            cout << setw(3) << iRow << "  ";
            for (int iCol = 3; iCol < 6; iCol += 0.5){
                cout << setw(8) << grid[iRow][iCol];
            }
            cout << endl;
        }
        
        //Asking user if they would like to run again
        cout << "Would you like to enter in another amount?: ";
        cin >> answer;
        if (answer == 'n' || 'N'){
            cout << "Bye" << endl;
            break;
        }
        break;
    }

}
baked turkey (4)
If this helps any, this is what my program should look like. Sorry for bad formatting, the forum won't keep the original (underscores are spaces).

Monthly Payment Calculator

Loan amount: 500000.00

Year _ 3.0% _ 3.5% ____ 4.0% ___ 4.5% ___ 5.0% _____ 5.5%
15 _ 3452.91 _ 3574.41 _ 3698.44 _ 3824.97 _ 3953.97 _ 4085.42
20 _ 2772.99 _ 2899.80 _ 3029.90 _ 3163.25 _ 3299.78 _ 3439.44
25 _ 2371.06 _ 2503.12 _ 2639.18 _ 2779.16 _ 2922.95 _ 3070.44
30 _ 2108.02 _ 2245.22 _ 2387.08 _ 2533.43 _ 2684.11 _ 2838.95

Loan amount: 0

Bye!
Last edited on
salem c (3700)
>while (answer == 'y' || 'Y')
You wrote
while (answer == 'y' || 'Y' != 0)

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        int grid [4][6] = {0};
        
        for (int iCol = 3; iCol < 6; iCol += 0.5){
            for (int iRow = 15; iRow < 33; iRow +=5 ){
                grid[iRow][iCol] = monthlyPayment;
            }
        }

You might be going round the loops 4 and 6 times respectively, but those aren't the indices you're writing to.
You're trashing memory way outside your array.

> for (int iCol = 3; iCol < 6; iCol += 0.5)
Adding .5 to an int is likely to leave it unmoved.
3 + 0.5 is still 3 (as an integer)

> grid[iRow][iCol] = monthlyPayment;
You probably want some variable result, say
monthlyPayment = loanAmount * monthlyRate / (1 - 1 / pow((1 + monthlyRate), months));

Not fill the array with the same answer.
keskiverto (10402)
Furthermore, your code:
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double monthlyRate; // uninitialized variable; value is unknown

// monthlyRate is not touched

monthlyPayment = loanAmount * monthlyRate / (1 - 1 / pow((1 + monthlyRate), months));

You can't use montlyRate's value before you set it. salem c hinted that it might be different on each column.


A detail, not an error, is that C/C++ are row-major. That is, if there is 2D array:
abc
def

then it is actually in continuous block of memory:
abcdef

A column-major language would put data:
adbecf

On large arrays in some hardware there can be performance difference between:
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        for (int iCol = 3; iCol < 6; iCol += 0.5){
            for (int iRow = 15; iRow < 33; iRow +=5 ){
                grid[iRow][iCol] = monthlyPayment;
            }
        }

and
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        for (int iRow = 15; iRow < 33; iRow +=5 ){
            for (int iCol = 3; iCol < 6; iCol += 0.5){
                grid[iRow][iCol] = monthlyPayment;
            }
        }

But as already said, indices are calculated wrong in these.
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