Go4Expert - atoi/atof problem

Go4Expert (http://www.go4expert.com/)

- C (http://www.go4expert.com/forumdisplay.php?f=20)

- - atoi/atof problem (http://www.go4expert.com/showthread.php?t=21293)

atoi/atof problem

How will I capture a string or char input if I have a checker that is equated to zero
because atoi/atof reads the string or char as zero

Code:

#include <stdio.h>

#include <conio.h>

#include <math.h>

#include <stdlib.h>

#include <string.h>



int a(double sales,double sepcost)

{

    double NRV;

    NRV=sales-sepcost; 

    printf("The Net Realizable Value is: %.3lf\n",NRV);



}

int main()

{

    double sales,sepcost;

    char error[128];

  

    do{

      system("cls");

      printf("Please input your Sales Value: \n");

      scanf("%s",&error);

      sales=atof(error);

      printf("Please input your Separable Cost: \n");

      scanf("%s",&error);

      sepcost=atof(error);

      if(sales<0){

        system("cls");

        printf("Invalid input for Sales, Please try again!!\n");

        system("pause");

        }

      if(sepcost<0){

        system("cls");

        printf("Invalid input for Seperabe Cost, Please try again!!\n");

        system("pause");

        }

      }while(sales<0||sepcost<0);

      a(sales,sepcost);



getch();

}

Re: atoi/atof problem

atoi and atof function will return the converted values.

your checking the return value is 0 or not. instead of you can check the given string is digit or not using isdigit() or isalpha()

Re: atoi/atof problem

How to do that?I don't know how to use the ctype.h

Re: atoi/atof problem

isdigit takes a char parameter and returns TRUE or FALSE depending on whether it's a digit or not. So the following will output 01:

Code:

printf("%c%c", isdigit('x')?'1':'0', isdigit('3')?'1':'0');

To determine whether input is valid you have to scan the string and see what you find. "123a456" is not a valid integer because 'a' is not a digit. "-2.35e+17" is a valid floating point number and the validation for that is more complex: optional sign, a digit, a dot, some digits, an e, optional sign, some digits.