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Switch case with String not working!

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Switch case with String not working!

 
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  #1
Jun 19th, 2009
the following is a simple program that fragments standardized name consisting of 3 letters and 2 numbers then prints the full word, for instance spa11 print spanish eleven.

Why is it not working?


c Syntax (Toggle Plain Text) 
  1. char sname[4];
  2. char snum[3];
  3.  
  4. // void strnumCpy(char *dest, char *source) { // NOT ACCURATE
  5. void strNumCpy(char *dest, const char *source) { // You are passing a const char in the source parameter, not a regular char.
  6.   int i=0;
  7.   do { // Isn't it easier to use a for loop here ? :)
  8.     *source++;
  9.     i += 1;
  10.   } while (i < 3);
  11.   while (*source)
  12.     *dest++ = *source++ ;
  13.   *dest = 0; // This adds the null terminator
  14. }
  15.  
  16. void look_up(char *fname)
  17. {
  18.  
  19.   strncpy(sname, fname, 3);
  20.   sname[3] = 0;
  21.   strNumCpy(snum, fname);
  22.   read_sname(sname);
  23.   read_snum(snum);
  24.  
  25. }
  26.  
  27. void read_sname(char *snm)
  28. {
  29.      switch(snm)  {
  30.  
  31.      case "ara": printf("\n%s\n", 'arabic'); break;
  32.      case "spa": printf("\n%s\n", 'spanish'); break;
  33.      case "eng": printf("\n%s\n", 'english'); break;
  34.      case "bio": printf("\n%s\n", 'biology'); break;
  35.      case "ger": printf("\n%s\n", 'german'); break;
  36.  
  37.      }
  38.  
  39. }
  40.  
  41. void read_snum(char *sno)
  42. {
  43.  
  44.      switch(sno)  {
  45.  
  46.      case "01": printf("\n%s\n", 'one'); break;
  47.      case "02": printf("\n%s\n", 'two'); break;
  48.      case "03": printf("\n%s\n", 'three'); break;
  49.      case "05": printf("\n%s\n", 'five'); break;
  50.      case "11": printf("\n%s\n", 'eleven'); break;
  51.  
  52.      }
  53.  
  54. }
  55.  
  56. void main()
  57. {
  58.  
  59.   look_up("spa02");
  60.   look_up("eng11");
  61.   look_up("ger05");
  62.  
  63. }
Last edited by Tekmaven; Jun 19th, 2009 at 7:19 pm. Reason: Code Tags
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Re: Switch case with String not working!

 
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  #2
Jun 19th, 2009
There are several problems but first of all your source strings are how long? And you're stuffing them into a buffer how long?

5 + 1 chars in 4 char buffer. What about the last character and the terminator?

Do you mean to intentioning destroying the 1st digt of the source data by setting the terminator after the first three letters of ASCII.

Don't forget ASCIIz strings have a hidden ('\0') terminator.

Correct and repost!


Note: Use stack buffers and make them much larger then needed. Won't cost you anything!
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Re: Switch case with String not working!

 
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  #3
Jun 19th, 2009
Oh and while you're at it! Fix your case statement!

Each case condition is an integer value (enum) only!
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Re: Switch case with String not working!

 
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  #4
Jun 19th, 2009
It would be more correct to say that switch case only works for integer constants

To the OP:
Read this before posting!
"Never argue with idiots, they just drag you down to their level and then beat you with experience."
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Re: Switch case with String not working!

 
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  #5
Jun 19th, 2009
as already stated, never try to use strings as cases for a switch. Some languages (like Perl) will allow this. C will not.

you could, for instance, try something like this:

c Syntax (Toggle Plain Text) 
  1. void read_snum(char *sno)
  2. {
  3.    int courseNum;
  4.    courseNum = atol(sno);
  5.  
  6.    switch(courseNum)
  7.    { 
  8.       case 1: printf("\n%s\n", 'one'); break;
  9.       case 2: printf("\n%s\n", 'two'); break;
  10.       case 3: printf("\n%s\n", 'three'); break;
  11.       case 5: printf("\n%s\n", 'five'); break;
  12.       case 11: printf("\n%s\n", 'eleven'); break;
  13.  
  14.       default: printf("\nInvalid Course Number\n");
  15.    }
  16. }

note, that my use of atol employs no error checking. I'm just using this as an example for switch/case statement. the preferred method would be strtol() and verify the string contains a valid number before moving to the switch.

.
Last edited by jephthah; Jun 19th, 2009 at 5:48 pm.
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Re: Switch case with String not working!

 
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  #6
Jun 20th, 2009
switch(expression) - where expression must be of int or char data type.
Failure is not fatal, but failure to change might be. - John Wooden
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Re: Switch case with String not working!

 
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  #7
Jun 20th, 2009
Hey jephthah, since when can we use single quotes for c-strings?
C Syntax (Toggle Plain Text) 
  1. case 1: printf("\n%s\n", 'one'); break;
  2. case 2: printf("\n%s\n", 'two'); break;
  3. case 3: printf("\n%s\n", 'three'); break;
  4. case 5: printf("\n%s\n", 'five'); break;
  5. case 11: printf("\n%s\n", 'eleven'); break;
"Never argue with idiots, they just drag you down to their level and then beat you with experience."
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Re: Switch case with String not working!

 
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  #8
Jun 20th, 2009
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Originally Posted by tux4life View Post
Hey jephthah, since when can we use single quotes for c-strings?
C Syntax (Toggle Plain Text) 
  1. case 1: printf("\n%s\n", 'one'); break;
  2. case 2: printf("\n%s\n", 'two'); break;
  3. case 3: printf("\n%s\n", 'three'); break;
  4. case 5: printf("\n%s\n", 'five'); break;
  5. case 11: printf("\n%s\n", 'eleven'); break;
oh, hell, i just cut and pasted his code. i didn't even notice that

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Re: Switch case with String not working!

 
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  #9
Jun 20th, 2009
Hey Guys, Thanks alot for all your replies, here is a corrected version of the code.
C Syntax (Toggle Plain Text) 
  1. #include <stdio.h>
  2. #include <string.h>
  3.  
  4. //Razan Sadeq
  5. //Blind Student Study Helper Project
  6. //PIC16F877A is used with 4 MHz oscillator
  7. //vmusic2 is used and connected to USART module.
  8. //Modified by N.A.
  9.  
  10. char sname[4];
  11. char snum[3];
  12.  
  13.  
  14. void strNumCpy(char *dest, const char *source) { 
  15.   int i=0;
  16.   do { 
  17.     *source++;
  18.     i += 1;
  19.   } while (i < 3);
  20.   while (*source)
  21.     *dest++ = *source++ ;
  22.   *dest = 0; // This adds the null terminator
  23. }
  24.  
  25. void read_sname(char *snm)
  26. {
  27. 	char s = *snm;
  28.      switch(s)  {
  29.  
  30.      case 'a': printf("\n%s\n", "arabic"); break;
  31.      case 's': printf("\n%s\n", "spanish"); break;
  32.      case 'e': printf("\n%s\n", "english"); break;
  33.      case 'b': printf("\n%s\n", "biology"); break;
  34.      case 'g': printf("\n%s\n", "german"); break;
  35.  
  36.      }
  37.  
  38. }
  39.  
  40. void read_snum(char *sno)
  41. {
  42.  
  43. 	if (!strcmp(sno,"01"))
  44. 		printf("\n%s\n", "one");
  45. 	else if (!strcmp(sno,"02"))
  46. 		printf("\n%s\n", "two");
  47. 	else if (!strcmp(sno,"03"))
  48. 		printf("\n%s\n", "three");
  49. 	else if (!strcmp(sno,"05"))
  50. 		printf("\n%s\n", "five");
  51. 	else if (!strcmp(sno,"11"))
  52. 		printf("\n%s\n", "eleven");
  53.  
  54. }
  55.  
  56. void look_up(char *fname)
  57. {
  58.  
  59.   strncpy(sname, fname, 3);
  60.   sname[3] = 0;
  61.   strNumCpy(snum, fname);
  62.   read_sname(sname);
  63.   read_snum(snum);
  64.  
  65. }
  66.  
  67.  
  68.  
  69. void main()
  70. {
  71.  
  72.   look_up("spa02");
  73.   look_up("eng11");
  74.   look_up("ger05");
  75.  
  76. }
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Re: Switch case with String not working!

 
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  #10
Jun 20th, 2009
Don't use void main() !!!!!!!!
Read this if you don't understand why
"Never argue with idiots, they just drag you down to their level and then beat you with experience."
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