Check??Newbie..HELP!!

This is a discussion on Check??Newbie..HELP!! within the C++ Programming forums, part of the General Programming Boards category; Hi, Its a newbie Q!!please help........ I want to check if the integers entered are only numbers ,not strings/characters. I ...

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    Check??Newbie..HELP!!

    Hi,

    Its a newbie Q!!please help........
    I want to check if the integers entered are only numbers ,not strings/characters.

    I know isdigit function but i suppose its in character-handled library,but I am using class string.So is there any function for checking that input values are only integers not character/strings/symbols etc;


    thanks

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    scanf("%d", varname);

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    Unhappy thanks...but

    Hi,

    thanks for replying, but i assume, u gave me a soln in c and not vc++,
    if,iam not wrong??I am unsure though.........
    thankx

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    yes it is C but it works just as well in C++. the header file is conio.h

    or at least it works on MY VC++, 4.0 that is

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    you could do it manually... personally, i dont use the string data tye cuz it takes away all your power (muwhahaha). anywayz, use a char array and check the contents:
    Code:
        int i;
        char s[100];
        cin.getline( s, '\n' );
    
        for( i = -1; i != strlen( s ) + 1; i++ ){          
    //strlen checks the length of the string
            if( s[i] != '1' && s[i] != '2' && s[i] != '3' ){
                //your string has a symbol or whatever
                //this just check 1, 2, and 3, but you get the point (i hope)
                .
                .
                .
                break;     //breaks out of the for loop
            }
         }
    remember to include string.h
    im probably gonna receive some criticism for this post because some ppl might think the code "inefficient", but computers now are like 2ghz. welcome to reality folks!

    also, scanf is stdio.h not conio.h
    Last edited by Flikm; 04-06-2002 at 10:45 PM.

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    geek SilentStrike's Avatar
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    Yeah.. instead of using the string class, you post O(n^2) code for something that could trivially be O(N) .
    Prove you can code in C++ or C# at TopCoder, referrer rrenaud
    Read my livejournal

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    ????

    Hi,
    I dont understand what SilentStrike is tryin to say????
    Btw,thanks flikm and denethor2000
    But as this an assignment, its expected to use a string and not char array.......also only c++ will be allowed for obvious reasons...
    So can anyone please tell me how to check if the value entered is an integer and not strings/char/symbols???
    thanks..........

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    Unhappy Please help!

    32 reads!!!still waiting!!!!!

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    >>32 reads!!!still waiting!!!!!

    ...meanwhile do a search on the board for integer input check... it might help

  10. #10
    Registered User Invincible's Avatar
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    If you absoloutely have to have a string you can always typecast a character array into a string.

    Code:
    (string) char;
    "The mind, like a parachute, only functions when open."

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    if I haven't misunderstood your request, here is a nifty little while loop that clears and ignores the information that was in the buffer and does exactly what you want...the only thing it will accept is numbers

    Code:
    int num;
    
     cout <<"pls enter num";
     cin >> num;
    
     while (cin.fail())
     {
        cin.clear();
        cin.ignore (BUFFER, '\n');
        cout << "\n pls re-enter number";
        cin >> num;
     }
    NB: dont forget to create a BUFFER constant, that is :
    const int BUFFER=128; before main.

    sophie
    simple is always an understatement.....

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    Smile thanks a bunch

    Hi sophie,
    it worked liked a charm......thanks a lot
    but can u enlighten me about what buffer=128 ,cin.clear(),cin.fail(),cin.ignore() funcns do??????
    thanks once again.

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    firstly, Im glad you found what you were after as for what they do.

    the buffer constant you declared can be any size...I usually use 128...just like the sound of it the cin.fail() condition checks and returns a value, that is if the input was anything other than a number cin.fail() would return true (which is the condition for entering a loop).

    the cin.clear() and cin.ignore() does exactly as they say...they ignore and clear the buffer thus cin >> num will have a clean and empty buffer to get info from.

    sophie
    simple is always an understatement.....

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    Thumbs up ok!got it!!

    thanks,
    I got it!!!!!!!!!

  15. #15
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    Question another dumb Q

    Hi,
    is there any function like cin.fail() to check for the input value is only string and not numbers??????/
    thanks..........

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