AboutPrince M. Premnath Expertise Years of research in Turbo C 3.0 Will bring you all facts regarding , OOPS , SVGA , MOUSE , BIOS , IVT , Be free to ask questions.
Expert: Prince M. Premnath Date: 4/15/2008 Subject: Input Validation in C++
Question QUESTION: how to validate user input? only double precision and integer are allowed.
This should not be allowed:
1. 123th...
2. _===\\
3. uuu67
This will be allowed
1. +67.89
2. -67.89
3. 67.89
4. 20
Please make a small program of this because I really find it hard... Thanks
ANSWER: Hi Dear Jade !
A simple approach is just read the input as a string; scan the string , if you find any anomaly then report with an error , else if it found to be a valid integer of a float number then convert the string into integer and float using the built in functions atoi() and atof() respectively .
Tip : To identify float from integer before converting , just make sure if you encountered with a '.' symbol then use float ie atof() function to convert otherwise use atoi()
Thanks and Regards !
Prince M. Premnath
---------- FOLLOW-UP ----------
QUESTION: can you make a simple code out of this, i'm really confused
Answer Dear Mr Jade !
Presenting you a simple code just to read a string and then convert into integer !
If it found to be a valid number , then the conversion will return the string as an integer else it will return 0 , same in case of float conversion !
You can add more constraints with this basic code.
#include<iostream.h>
#include<stdlib.h>
void main()
{
int ino;
float fno;
char buffer[8];
cout<<"Enter a number";
cin>>buffer;
ino = atoi(buffer);
if(!ino)
cerr<<"Error input in number ";
else
cout<<ino;
