Thread: Replacing switch statement with a nested if/else

Originally Posted by CommonTater

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

That's not true.
Aren't if-else statements something that you would learn in about your first week programming? Back to the books man.

Thanks all for your help. I am learning C on my own, still on the loop control chapters and I'm using Code Block with mingw as compiler.

I have added this line to deal with space and newline:

Code:

else if ( grade == '\n' || grade == ' ' )
     continue;

Here's the full exercise:

Rewrite the program of Fig. 4.7 by replacing the switch statement with a nested if/else statement, be careful to deal with the default case properly. The rewrite this new version by replacing the nested if/else statement with a series of if statements; here too, be careful to deal with the default case properly (this is more difficult than in the nested if/else statement version). This exercise demonstrates that switch is a convenience and that any switch statement can be written with only single-selection statements.

fig. 4.7:

Code:

/* Fig. 4.7: fig04_07.c
   Counting letter grades */
#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;
}



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Create a boolean flag that is set to true, e.g., use an int variable initialised to 1. Set this boolean flag to false for each case (e.g., assign 0 to the int variable). Use this flag to check for the default case.

My code below. My biggest inspiration for solving this was due to Rags_to_Riches and laserlight suggestions. Also I found out, the initial problem at hand was not-so-trivial.

My biggest problem was, that I thought the EOF for my home system was ( ctrl^C + Enter ).

It wasn't. I just found out by accident, that it's ( ctrl^z + Enter). I've spent many hours thinking that the code was wrong, when I was only using the wrong escape sequence.

Anyway, I learned a lot from this, and spent the last day pushed back to the beginning pages
of my C book - dealing with keyboard input.

I'm saving this code for future reference.

Code:

#include <stdio.h>

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

   char junk[80];

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

   while ( (grade = fgetc(stdin)) != EOF )	// on my home system, EOF character is invoked
   {								// by  ( ctrl^z + ENTER ) sequence
      if ( grade == 'A' || grade == 'a' )
     {
	     aCount++;
		  getchar();	// chomps out the extra '\n'  per Rags_To_Riches
      }

      else if ( grade == 'B' || grade == 'b' )
      {
            bCount++;
	    getchar();
       }

      else if ( grade == 'C' || grade == 'c' )
     {
         cCount++;
	 getchar();
     }

      else if ( grade == 'D' || grade == 'd' )
      {
           dCount++;
	   getchar();
      }

      else if ( grade == 'F' || grade == 'f' )
      {
           fCount++;
	   getchar();
       }

      else
      {
          printf( "Incorrect letter grade entered." );
          printf( " Enter a new grade.\n" );		
	  gets(junk);	// gets rid of many extra chars
      }

   }

   printf( "\nTotals for each letter grade are:\n\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 );

   printf("\n\n");
   return 0;
}

You have no idea how much "junk" there is in the input buffer! This is a time bomb!