Function prototype difficulties

Question

I am having difficulties in getting my program working properly. For the part of the project I am having difficulties with, I need to create a function that validates two different numbers input by the user. However in the whenever I run the program I get two errors going on.

One is that the input is first read as me inputting 0 (even though I didn't)

And the second is that it treats it runs the first input through the second inputs validation test

Function prototypes:

int validate(int , int);

Main:

do
{       
    //display the menu
    displayMenu();
    cin >> choice; 
    validate(choice, months);

    // process the user's choice
    if (choice != QUIT_CHOICE)
    {
        // get the number of months
        cout << over3 << "For how many months? ";
        cin >> months; 
        validate(choice, months);
}

And the function prototype in question:

int validate(int choice, int months)
{
while (choice < 1 || choice > 4)
{
    cout << over3 << choice << " is not between 1 and 4! Try again: ";  
    cin >> choice;
}

while (months < 1 || months > 12)
{
    cout << over3 << months << " is not between 1 and 12! Try again: "; 
    cin >> months;
}

}

score 0 · Accepted Answer · answered Apr 09 '14 at 18:04

0

Since both of them are independent of each other, you need to separate the into two functions for your purpose : validateChoice which consists of the first while loop and validateMonths which consists of second while loop.

If you want single function itself you need to pass appropriate parameter

int validate(int value, int lowLimit, int HighLimit)
{
    while(value < lowLimit || value > HighLimit)
    {
        //print error message here
        cin>> value;
    }
    return value;
}

In main, do

cin >> choice;
choice = validate(choice, 1, 4);

Similarly for months.

answered Apr 09 '14 at 18:04

GoldRoger

1,263
7
10

The correct way to use a `std` stream for reading is `if(cin >> value) { /* do something with value */ } else { /* failure to read */ }`. You still perform a formatting read without checking it if succeeded. – pmr Apr 09 '14 at 18:07
okay thats what i think I 'm going to have to do.. my professor says to use a function named validate to validate both of those values but I really have no idea how to do that – Tyler Kelly Apr 09 '14 at 18:08
@user3470987 Isn't my answer showing you same thing ? Function called `validate` which validates both values. You just need to pass different arguments during different function calls. – GoldRoger Apr 09 '14 at 18:11
oh okay okay i gotcha, that kinda makes sense kinda. do you know what pmr means? – Tyler Kelly Apr 09 '14 at 18:17
He is asking you to check if the read is successful. Check [this](http://stackoverflow.com/a/5695176/2829267) – GoldRoger Apr 09 '14 at 18:21

score 0 · Answer 2 · answered Apr 09 '14 at 18:07

You haven't shown how (if at all) you initialize choice and months before your do loop, but my guess is you haven't. Therefore here:

cin >> choice; 
validate(choice, months);

You are passing an uninitialized value as the second argument to validate. An uninitialized value could be anything; in your case, it seems to be zero.

Function prototype difficulties

2 Answers2