Use the character classification functions to prepare an implementation of atoi() - C String

C examples for String:String Function

  1. HOME
  2. C
  3. String
  4. String Function

Description

Use the character classification functions to prepare an implementation of atoi()

Demo Code

#include <stdio.h>
#include <ctype.h>

int my_atoi(char *string);

int main(int argc, char *argv[]){
  int input;//  www. j  a  v  a  2 s  .  com

  if (argc != 2)
    puts("Usage: <program_name> <arg_1>");
  else
  {
    input = my_atoi(argv[1]);
    printf("%d + 5 = %d\n", input, input + 5);
    printf("%d / 2 = %d\n", input, input / 2);
    printf("%d %% 3 = %d\n", input, input % 3);
  }

  return 0;
}

int my_atoi(char *string){
  int total = 0;

  while (*string != '\0')  {
    if (!isdigit(*string))
      // string is not a pure integer -- return 0
      return 0;
    else{
      total *= 10; // shift digits one place to left
      total += *string - '0'; // add newest digit in ones place
    }

    string++;
  }

  return total;
}

Related Tutorials