Thread: how to read in octal

I am creating a simple calculator to do simple math in dec hex and octal froms , i am having trouble reading in an argument as a octal value, my hex is working fine when I enter 0x before the number but when reading in 010 for 8 in octal it just reads in 10, any suggestions?

Code:

#include<stdio.h>
#include <stdlib.h>
#include<string.h>
int main(int argc, char *argv[]){
  int a;
  int b;
  int c;
  int i;


  if  (argc  == 4 || (strcmp (argv[4], "dec") == 0 )){
    if (strcmp (argv[2], "+") == 0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a+b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "-")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a-b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "*")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a*b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "/")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a/b;
      printf("%d\n", c);}
    if (strcmp (argv[2], "%")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a%b;
      printf("%d\n", c);}}

  if (argc == 5){
 if  ((strcmp (argv[4], "oct") == 0 )){
    if (strcmp (argv[2], "+") == 0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c=a+b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "-")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a-b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "*")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a*b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "/")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a/b;
      printf("%o\n", c);}
    if (strcmp (argv[2], "%")==0){
      a = atof(argv[1]);
      b = atof(argv[3]);
      c= a%b;
      printf("%o\n", c);}}

 if  ((strcmp (argv[4], "hex") == 0 )){
   if (strcmp (argv[2], "+") == 0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c=a+b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "-")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a-b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "*")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a*b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "/")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a/b;
     printf("%x\n", c);}
   if (strcmp (argv[2], "%")==0){
     a = atof(argv[1]);
     b = atof(argv[3]);
     c= a%b;
     printf("%x\n", c);}}
  }

return 0;
}

thanks

Read it as a string and parse from there. Scanf doesn't support octal(AFAIK) and it isn't too hard to convert anyway.

Originally Posted by User Name:

Read it as a string and parse from there. Scanf doesn't support octal(AFAIK) and it isn't too hard to convert anyway.

im not using scanf, we were told not to i am reading them in as arguments

Sorry, didn't RTFS.

Okay... The problem is with atof. You'll have to implement your own I guess. For octal:

Code:

int octal(char *num)
{
     int total = 0;
     for(int digit = 0;num[digit] != '\0';digit++)
          total += (num[digit] - '0') * (int)pow(8, strlen(num) - (digit + 1));

     return total;
}

Is your class at a point where this would be reasonable, or is this "too advanced" and they are likely looking for something else?

Originally Posted by User Name:

Sorry, didn't RTFS.

Okay... The problem is with atof. You'll have to implement your own I guess. For octal:

Code:

int octal(char *num)
{
     int total = 0;
     for(int digit = 0;num[digit] != '\0';digit++)
          total += (num[digit] - '0') * (int)pow(8, strlen(num) - (digit + 1));

     return total;
}

Is your class at a point where this would be reasonable, or is this "too advanced" and they are likely looking for something else?

sounds a little complicated but not aweful, is there no simpler way?

>> Scanf doesn't support octal(AFAIK)

Use %o -- see this page for a source.