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Only accept an alphabetical character

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Join Date: Nov 2007

Posts: 66

Reputation: superjacent is an unknown quantity at this point

Solved Threads: 3

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Re: Only accept an alphabetical character

#11

Apr 15th, 2008

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Originally Posted by jade09091990

the code actually has a bug, for example you've entered something like this: c2,
the program will behave unexpectedly, how to remedy this?

Good pick up. It appears that the variable ch needs to be checked prior to the switch statement. I've modified my original program that I posted at the top of this thread. What needed to be done is simply make sure that the next character was a newline, if it was then only a single character was input. If the next character wasn't a newline then something like c2 was entered.

Here's the code:

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// chap06q03.cpp  
// C++ Primer Plus, Fifth Edition
// Chapter 6, Page 276.
// Programming Exercise # 3
// 4 Dec, 2007.
// 15 Apr, 2008 - modified - disregarding c2 etc.
 
#include <iostream>
 
int main()
{
    using namespace std;
    char ch;
    char msg[] = "\nPlease enter  c, p, t or g: ";
    bool invalid = true;
 
    cout << "Please enter on of the following choices:\n\n";
    cout << "c) carnivore        p) pianist\n";
    cout << "t) tree             g) game\n";
 
    while (invalid)
    {
        cin >> ch;
        if ((ch != 'c') && (ch != 'p') && (ch != 't') && (ch != 'g'))
        {
            while (cin.get() != '\n')
                continue;
            cout << msg;
        }
        else
            if (cin.get() == '\n')
                 invalid = false;
            else
            {
                while (cin.get() != '\n')
                    continue;
                cout << msg;
            }
    }
    switch (ch)
    {
        case 'c' : cout << "Option 'c' selected"; break;
        case 'p': cout << "Option 'p' selectd";break;
        case 't' : cout << "Option 't' selected";break;
        case 'g': cout << "Option 'g' selected"; break;
        default : cout << "It will never get her"; break;
    }
    // exit routine
    cout << "\n\n...Press ENTER to Exit System...";
    cin.get();
    return 0;
}
// chap06q03.cpp  
// C++ Primer Plus, Fifth Edition
// Chapter 6, Page 276.
// Programming Exercise # 3
// 4 Dec, 2007.
// 15 Apr, 2008 - modified - disregarding c2 etc.

#include <iostream>

int main()
{
    using namespace std;
    char ch;
    char msg[] = "\nPlease enter  c, p, t or g: ";
    bool invalid = true;
	
    cout << "Please enter on of the following choices:\n\n";
    cout << "c) carnivore        p) pianist\n";
    cout << "t) tree             g) game\n";
	
    while (invalid)
    {
        cin >> ch;
        if ((ch != 'c') && (ch != 'p') && (ch != 't') && (ch != 'g'))
        {
            while (cin.get() != '\n')
                continue;
            cout << msg;
        }
        else
            if (cin.get() == '\n')
                 invalid = false;
            else
            {
                while (cin.get() != '\n')
                    continue;
                cout << msg;
            }
    }
    switch (ch)
    {
        case 'c' : cout << "Option 'c' selected"; break;
        case 'p': cout << "Option 'p' selectd";break;
        case 't' : cout << "Option 't' selected";break;
        case 'g': cout << "Option 'g' selected"; break;
        default : cout << "It will never get her"; break;
    }
    // exit routine
    cout << "\n\n...Press ENTER to Exit System...";
    cin.get();
    return 0;
}

Given some time I'm sure the above program can be smoothed out, but at least it demonstrates only accepting a single character (not using strings and other methods). As it stands now, clearly there are a couple of snippets which are candidates to be functions.