Thread: Replacing switch statement with a nested if/else

I have to replace the switch statement with a nested if/else of this program:

Code:

#include <stdio.h>

int main()
{
   int grade;
   int aCount = 0, bCount = 0, cCount = 0, 
       dCount = 0, fCount = 0;

   printf(  "Enter the letter grades.\n"  );
   printf(  "Enter the EOF character to end input.\n"  );

   while ( ( grade = getchar() ) != EOF ) {

      switch ( grade ) {    /* switch nested in while */

         case 'A': case 'a':  /* grade was uppercase A */
            ++aCount;         /* or lowercase a */
            break;

         case 'B': case 'b':  /* grade was uppercase B */
            ++bCount;         /* or lowercase b */
            break;

         case 'C': case 'c':  /* grade was uppercase C */
            ++cCount;         /* or lowercase c */
            break;

         case 'D': case 'd':  /* grade was uppercase D */
            ++dCount;         /* or lowercase d */
            break;

         case 'F': case 'f':  /* grade was uppercase F */
            ++fCount;         /* or lowercase f */
            break;

         case '\n': case' ':  /* ignore these in input */
            break;

         default:        /* catch all other characters */
            printf( "Incorrect letter grade entered." ); 
            printf( " Enter a new grade.\n" ); 
            break;
      }
   }

   printf( "\nTotals for each letter grade are:\n" );
   printf( "A: %d\n", aCount );
   printf( "B: %d\n", bCount );
   printf( "C: %d\n", cCount );
   printf( "D: %d\n", dCount );
   printf( "F: %d\n", fCount );

   return 0;
}

This is my work:

Code:

#include <stdio.h>

int main()
{
   int grade;
   int aCount = 0, bCount = 0, cCount = 0,
       dCount = 0, fCount = 0;

   printf(  "Enter the letter grades.\n"  );
   printf(  "Enter the EOF character to end input.\n"  );

   while ( ( grade = getchar() ) != EOF )
   {
      if ( grade == 'A' || grade == 'a' )
         ++aCount;
      else if ( grade == 'B' || grade == 'b' )
         ++bCount;
      else if ( grade == 'C' || grade == 'c' )
         ++cCount;
      else if ( grade == 'D' || grade == 'd' )
         ++dCount;
      else if ( grade == 'F' || grade == 'f' )
         ++fCount;
      else
      {
         printf( "Incorrect letter grade entered." );
         printf( " Enter a new grade.\n" );
      }

   }

   printf( "\nTotals for each letter grade are:\n" );
   printf( "A: %d\n", aCount );
   printf( "B: %d\n", bCount );
   printf( "C: %d\n", cCount );
   printf( "D: %d\n", dCount );
   printf( "F: %d\n", fCount );

   return 0;
}

I have problem with replacing the default with else. When I input grades (a,b,c,d,f) , it still print the else statement.

It's reading the newline immediately after the grade. If you enter "a", the input buffer has "a\n", so add another getchar() just before the if/else (and don't do anything with the value...just ignore it) to eat the newline.

Apparently the people who made the standard were not intelligent enough to add a standard way to flush stdin

How to flush stdin? stdin may be redirected from your harddrive? so fflush(stdin) becomes wiping your drive?
fflush() is for output files. When you open file with read mode, you can't modify it. So how should fflush(input_file) work?
You could try it out yourself use fflush(stdin) and redirect stdin to a file.

Code:

     else if ( grade == 'F' || grade == 'f' )
         ++fCount;
      else
      {
         printf( "Incorrect letter grade entered." );
         printf( " Enter a new grade.\n" );

You still need "else if" for your final clause.

Originally Posted by CommonTater

Code:

     else if ( grade == 'F' || grade == 'f' )
         ++fCount;
      else
      {
         printf( "Incorrect letter grade entered." );
         printf( " Enter a new grade.\n" );

You still need "else if" for your final clause.

Why do you think so? Are you saying this for all

Code:

if (...) {...} else if (...) {...} ... else {...}

sequences or is there something specific about this one?

Originally Posted by CommonTater

Code:

     else if ( grade == 'F' || grade == 'f' )
         ++fCount;
      else
      {
         printf( "Incorrect letter grade entered." );
         printf( " Enter a new grade.\n" );

You still need "else if" for your final clause.

Just curious, did you try to compile the change with your suggestion? When I read this,
I went scrambling back around 5 chapters in my C book to check this out. There I found out, that with multiple "else if" the last part of that structure ends with just an "else".

Originally Posted by dev123

I have to replace the switch statement with a nested if/else of this program:

If this is so, you can't do this because the code using switch() (the logic) is fatally flawed as well.

What blows my mind, is this assignment. The switch() code was designed to replace ugly code using too many ifs and else if conditions. The switch() code can turn ugly code into one of elegance and simplicity.

The assignment should have had you take a long if - else if structure and change it to using a switch construction.

The premise of the argument, "take this switch() code and convert it to code using if - else if" construction is false on the basis that the switch () code presented above is also fatally flawed.

Specifically, I take issue with:

Code:

while ( ( grade = getchar() ) != EOF )

and the rational behind this design.

I'd like to see the algorithm or pseudo code. I would not have taken a trivial task, such as summing different grades, and then printing out the result, as presented.

I won't even use switch.

Code:

if( strchr("abcdef",tolower(grade)) ) {
Count[ tolower(grade) - 'a' ];   
} else {
 ...
}