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Calculation using input from text file

Posted on 2012-04-01
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Last Modified: 2012-04-01
Good evening -
I am having some difficulty with a field that is being read from a text input file.   I need to determine if the value is an odd number.   However, when I try to calculate using the field I get sharing violations.   I've even moved it to another integer field, but I get lvalue errors.   Here's the code snippet below.   Am I using a pointer incorrectly here?

while ((fscanf(fpNumbr, "%d", &numbIn)) == 1)
{      
      oddno = fscanf(fpNumbr, "%d", numbIn);
      if (oddno % 2 == 0)
      printf("*");
      else
      printf("%d", oddno);
}
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Question by:mojeaux
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13 Comments
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37794355
The problem is that fscanf's return value is not the value you need to test against. Your scanned value will be in numbIn and not in oddno as written.

int oddno;
while ((fscanf(fpNumbr, "%d", &oddno)) == 1)
{      
      if (oddno % 2 == 0)
         printf("*");
      else
         printf("%d", oddno);
}
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37794360
I just removed the extra parenthesis.

int oddno;
while (fscanf(fpNumbr, "%d", &oddno) == 1)
{      
      if (oddno % 2 == 0)
         printf("*");
      else
         printf("%d", oddno);
}
0
 
LVL 45

Expert Comment

by:Kent Olsen
ID: 37794361
Hi Mo,

The while() loop continues to grab consecutive integers from the input stream.  In fact, it can grab only one because the character that terminates the number isn't skipped.  When the fscanf() function is called again, it starts with the character that ended the previous conversion, so it reads no values.

You need to skip all of the non-digit items (space, newline, etc.) before calling fscanf again.


Kent
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LVL 8

Expert Comment

by:Anthony2000
ID: 37794370
I didn't include all the original code, but here is part that reads and determines whether the number is odd/even.

I ran the modified code and here is what the output looked like:

code:

                  int oddno;
                  while (fscanf(fpNumbr, "%d", &oddno) == 1)
                  {      
                          printf("%d", oddno); // I added to see what came back from fscanf
                          if (oddno % 2 == 0)
                               printf("*\n");
                          else
                               printf("%d\n", oddno);
                  }


output:
.
.
.
Press any key to continue . . .
123456789123456789
12345678*
12345671234567
123456*
1234512345
1234*
123123
12*
11
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37794374
Hi Kent,

I thought fscanf worked as you stated, but it appears to be skipping the newlines?

Anthony
0
 

Author Comment

by:mojeaux
ID: 37794403
Hi Anthony -
Here's the full function... i've commented out some sections because I'm testing.  
void oddNumb(FILE *fpNumbr, int *numbIn)
{

/* LOCAL DECLARATIONS */

int oddno;

/* STATEMENTS */

while ((fscanf(fpNumbr, "%d", &numbIn)) == 1)
{      
      /*fscanf(fpNumbr, "%d", numbIn);
      if (oddno % 2 == 0)
      printf("*");
      else*/
      printf("%d", numbIn);
      printf("*");
}  

return;
}/*disyplays odd numbers from text file*/

Right now the ouptput displays the following:
123456789*12345678*1234567*123456*12345*1234*123*12*1

However, the display should be:
1*3*5*7*9 new line
1*3*5*7* new line
1*3*5*7new line
1*3*5* new line
1*3*5 new line
1*3* new line
1*3 new line
1* new line
1 new line

I'm reading from a text file that looks like
123456789
12345678
1234567
123456
12345
1234
123
12
1

Hi Kent - I read your comments and I'm not sure how to eliminate the new lines from being read by the fscanf statement.   Should I check for " "?  Is this what the program sees when it reads from the text file?

Thanks!!
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37794422
Ok, i see.

Here is what i think you need to understand. Fscanf is is reading the numbers not one character at a time but rather one number such as 123456789, 12345678, etc. Then it converts from ASCII to a integer representation of the numeruc characters. Do youunderstand?
0
 
LVL 32

Expert Comment

by:phoffric
ID: 37794430
>> I get sharing violations
>> oddno = fscanf(fpNumbr, "%d", numbIn);
>> Am I using a pointer incorrectly here?

No. You need &numbIn to make numbIn a pointer to an int.
0
 
LVL 8

Accepted Solution

by:
Anthony2000 earned 2000 total points
ID: 37794434
I think what you need to do is read a single character at a time, determine if it represent a number between 0-9, and then determine if it is odd or even. Be careful to skip over carriage returns and line feedcharacters.
0
 

Author Comment

by:mojeaux
ID: 37794438
Hi Anthony -  thanks for the clarification.   I understand how the fscanf is working now.  

Would it be easier if I wrote to the text file, placing a space between each number?  Would the fscan then recognize each interger?   Or would I then have to identify the spaces like Kent mentioned earlier?
0
 

Author Comment

by:mojeaux
ID: 37794442
I see your last post and it answered my question.  Thanks!
0
 

Author Closing Comment

by:mojeaux
ID: 37794444
Appreciate the help tonight.   Hopefully I can get this wrapped up soon.   =)
0
 
LVL 8

Expert Comment

by:Anthony2000
ID: 37794446
That sounds like an easy adjustment to try. I think adding a space will work.
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