Re: [Dev-C++] Checking data type

Let's see if I can lay this problem to rest.

First the type you want to use to store the number depends if you need =
to allow for fault detection. If weight is an int then the conversion =
from the typed in text is automatic, however if your user doens't enter =
a valid number then an error will occur. Fortunately you can detect the =
error, i.e.

int value;
cout << "Enter a value: ";
cin >> value;
if(cin.fail())
{
    // respond to failure here
}

This will detect if a non-number is typed, however if you type '50dgds' =
(or whatever) then the value 50 will be extracted and the remaining =
characters will be left in the stream (another cin for a string would =
get the 'dgds'). Remember that if the operation fails then the stream is =
left untouched (anything typed will still be there) and value is =
unchanged. Also the failure will need to be cleared to avoid it being =
redetected if your program continues i.e. cin.clear();

The alternative method is to get a string of some sort, either a C++ =
string or C style char array and then convert it yourself. Conversion =
isn't too hard cos you can use the atoi() function. The function atoi() =
will only convert until it reaches a character it can't convert so if =
you passed it the above string (50dgds) then you would still get 50, but =
if you want to have that as invalid then you can go through the string =
with something like this:

int size;
std::string value; // or char value[80];

// get your string here

size =3D value.length(); // or strlen(value);
for(int i =3D 0; i < size; ++i)
{
    if(!isdigit(value[i]))
    {
        // non digit found do whatever i.e. set a flag
        break; // or some other termination
    }
}

I'll leave you to figure out the rest of that. E-mail again if you need =
help.

As for getting a number with a char, it's only useful for a single digit =
number. You could get a sequence of chars and total up the number, but a =
string would be easier.

Hope this helps, Jason.

----- Original Message -----=20
From: "Exuss Draugas" <dra...@ce...>
To: <Dev...@li...>
Sent: Thursday, December 27, 2001 7:20 PM
Subject: [Dev-C++] Checking data type


>=20
>=20
>  Hi,=20
>=20
>  Yes, this code above works, but only when ONE(!) simbol is entered.=20
> If I try to enter "4kdkdkd", the output says that the digital number=20
> was entered. I can't use that code in this prototype:=20
>  =20
>  // int weight ??
>  // char weight ??
>  // string weight ??
>  // char[10] weight ??
>=20
>  do
>  {
>      cout << "Input Your weight:";
>      cin >> weight;
>      // Checking type of entered value
>      // because the program will crash, if value isn't digital number
>      // if value is not NUMBER cout << "Please, input number!";
>  } while ( /* value is bad */ )
> =20
>  // do some calculations with weight
> =20
>  Thanks,
>=20
>  Exuss
> =20
> =20
> >Your code was not proper ANSI C++ too. Your code corrected and fully
> >portable:
> >
> >
> >#include <cstdlib>
> >#include <cctype>
> >#include <iostream>
> >
> >int main()
> >{
> >    using namespace std;
> >
> > unsigned char number;
> >=20
> > cout << "\n\tInput number or letter: ";
> > cin >> number;
> >=20
> >     if(isalnum(number))
> >     {
> >      cout << "\n\tIt is alnum" <<endl;
> >      =20
> >        if(isdigit(number))
> >         cout << "\tIt is digit" <<endl;
> >     =20
> >        else if(isalpha(number))
> >        {
> >          cout << "\tIt is alpha" << endl;
> >        =20
> >          if(islower(number))
> >            cout << "\tIt is lower"<< endl;
> >        }
> >     }
> >    =20
> >     =20
> > cout << endl;
> >
> > system("PAUSE");
> >}
> >
> >
> >
> >Ioannis
> >
> >* Ioannis Vranos
> >* Programming pages: http://www.noicys.f2s.com
> >* Alternative URL: http://run.to/noicys
> >
> >
>=20
>=20
> --
> Nemokama el.pa=F0to d=EB=FEut=EB - http://webmail.delfi.lt/
>=20
> _______________________________________________
> Dev-cpp-users mailing list
> Dev...@li...
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