C++ Adding variables in if functions

Question

I'm doing rather beginner work with C++ and I am having a difficult time understanding what I am doing wrong with a simple program I am writing. So far, I have got the program written out some what properly, but I am confused on how to place variable place holders in IF Functions. Assuming of course, that is what is supposed to make it work properly.

To start with a little background on how the program is supposed to function. The user enters a 4-digit code and as long as the last digit of the code is a "7" it should display "Origin: Florida". Part two of the IF function would be, if the user enters a 4-digit number and the last digit of the code is a "4" it should display "Origin: California". I finished it with an else statement for any other entries to display "Invalid". The problem I am having is figuring out how to add variable digits for the first 3-digits of the code and when the last digit is entered with a "7" or "4" have a certain "Origin" displayed. I have searched and searched for guides on the interwebs for help, but I've had very little luck. If anyone could help me with this I would be very grateful for the assistance.

Below is the code I've written so with of course fault being in the IF statements:

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

int main()
{
    int Digits = 0;

    cout << " ..:::Grocery Program:::.. " << endl;
    cout << " ..::Created By Justin::.. " << endl;
    cout << "\n";   

    cout << " Enter the orange's 4-digit code: ";
    cin >> Digits;

    if ( Digits == 7 )
    {
        cout << " Origin: Florida ";
    }
    else if ( Digits == 0004 )
    {
        cout << " Origin: California ";
    }
    else
    {
        cout << " Origin: Invalid ";
    }

    cout << "\n";   
    cout << "\n";   
    cout << "\n";   
    cout << "\n";   
    cout << "\n";       
    system("pause");
    return 0;
}

It won't make a difference here, but 0004 is an octal literal, and equivalent to 04, which is just 4. Were you to do, say, 0014, it would have the value 12. — Qaz
– Qaz, Commented Feb 25, 2014 at 21:46
Is there a way to put placeholders or variables in the If Functions? So someone could enter 3324 or 1274 and it display the "Origin: Florida". — TranquilityByDesign
– TranquilityByDesign, Commented Feb 25, 2014 at 21:48
@TranquilityByDesign: If you have to work on codes that are more complex than simple numbers (say phonenumbers like +316-1111-2222), you'd use "Regular Expressions". Those have explicit placeholders. In this simple case, we could write the regular expression ^\d{3}4$ which means start with 3 digits, then a 4. As yu see, for simple examples regular expressions are a bit overkill. In C++ they're provided by the <regex> header. — MSalters
– MSalters, Commented Feb 26, 2014 at 10:12

user2033018 · Accepted Answer · 2014-02-25 21:49:48Z

1

A useful "trick" is to use the modulo (%) operator to get a number's digits. Say you want to get the last one...

int n = 1234;
int last_digit = n % 10; // last_digit == 4

To get the one next to the last, divide the number by 10 (which makes the last digit to go away) and do the same:

n /= 10;
int second_to_last = n % 10; // second_to_last == 3

answered Feb 25, 2014 at 21:49

user2033018

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2 Comments

TranquilityByDesign Over a year ago

It seems by doing that you can only receive the first number of the integer without bumping into doubles. I am looking in this case to have the last number of the 4-digit code to be the KEY in the equation that provides which answer to display. Such as, entering 1234 or 2234 or 5564 "Origin: Florida" and, entering 1237 or 2237 or 5567 "Origin: California". So no matter the first 3 #'s of the 4-digit code I need the last digit to be the determining factor of which message to display. Is there a type of variable I can use with absolute 4th digit

MSalters Over a year ago

@TranquilityByDesign: Computers don't store digits (base 10), they store bits (base 2). That's why you need the explicit % 10.

PBA · Accepted Answer · 2014-02-25 22:38:47Z

0

See if this helps: First, you may need to validate if the entered number of digits are 4, Something like this: // "number" is unsigned int so we remove the possibility of entering -ve number int digits = 0; while (number) { number /= 10; digits++; }

If the digits != 4 display invalid, otherwise check the last digit using the Modulo operator as mentioned by @Faranwath. Yes, and one more thing you need to save the number as you will need it later on to check the last digit.

answered Feb 25, 2014 at 22:38

PBA

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1 Comment

TranquilityByDesign Over a year ago

I'm sorry. I believe everyone is giving me wonderful answers to the problem, yet I have no clue how to implement that into what I am working on. I'll google around a bit for implementation and hopefully figure out what you guys mean lol Thank you for the help!

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