Can anyone help me think of just *how* I would check input to see if it's numeric. By the way, I'm using C++. I'll try to figure out the syntax on my own, but just some general ideas would help. Thanks.

Well, I'm thinking ascii codes...
Iterate though all the digits and check if their ascii values are within the certain 0-9 range....
pretty slow and inefficient but that's just me for you.

Yeah, a number is always of the form [+-]?[0-9]*(.[0-9]*)? in terms of regular expressions. That would be fairly to write by hand to check, or if there's an RE class that you have access to, then... yeah.

Or... scanf() and check that it returns nonzero (if memory serves)? Or atoi() and related functions.

- taubz

Or there is isalpha() maybe !isalpha() ?

isdigit() sounds better to me.

That'll be what I was looking for :-)

Hi,

It's very easy.. Here's example in java(it's easy to port that to C++):

for( int i=0;i<string.length();i++ )
{
char ch = string.charAt( i );

if( ch >= '0' && ch <= '9' )
{
// we know that current character is digit.
}
}

- method..

Even Java provides nice methods for character classifications!
java.lang.Character.isDigit()!

Yea I know that but I just tried to simulate how to do that without using a built-in structures.

- method..