switch case statement

I'm getting errors with the following switch case statement.

Code:

---

/*switch (command_read)
                {
                        case command_list[0]:
                        {
                                printf("Hello\n");
                        }
                        case command_list[1]:
                        {
                                printf("NHL\n");
                        }
                        case command_list[2]:
                        {
                                printf("NFL\n");
                        }
                        case command_list[3]:
                        {
                                printf("Kingston\n");
                        }
                        case command_list[4]:
                        {
                                printf("Eraser\n");
                        }
                }*/

---

I'm getting the following error:

Quote:

---

--------------------Configuration: IO - Win32 Debug--------------------
Compiling...
IO.CPP
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(71) : error C2051: case expression not constant
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(73) : error C2051: case expression not constant
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(75) : error C2051: case expression not constant
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(77) : error C2051: case expression not constant
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(79) : error C2051: case expression not constant
G:\Current Courses\EECE 314\projects\el_with_synchronization\IO\IO.CPP(81) : warning C4060: switch statement contains no 'case' or 'default' labels
Error executing cl.exe.

IO.exe - 5 error(s), 1 warning(s)

---

I'm not entirely sure about what's wrong with the implementation using the array indices. Any help would be much appreciated.

case labels should be constants
use enum for example

Right, the case-label needs to be an integer constant that the compiler knows at the compile-time. You are using an indexed array, which the compiler can't make into a constant at the time of compilation.

Vart suggests an enum, which is one good choice, e.g. :

Code:

---

enum somename {Value1, Value2, Value3};

  somename val;
...
  switch(val)
  {
      case Value1:
              ...
      case Value2:
              ...
      case Value3:
              ...
      default:
              ...
    }

---

If you have an array that contains some values, and you really want to switch on the content of the array, then you may want to use a loop to find the correct index and then switch on the index. Or you could make a two-element array:

Code:

---

struct st {
  int val;
  char *str;
};

static const st command_list[] =  {
  { 0, "Hello" },
  { 1, "NHL" },
  { 2, "NFL" },
  ...
};

...
  for(i = 0; i < sizeof(command_list) / sizeof(command_list[0]); i++)
  {
      if (command_list[i].val == command_read)
      {
          printf("%s\n", command_list[i].str);
          break;
      }
    }

---

There may be other solutions that are better for what you want to do, but without understanding what you are actually trying to achieve, this is the best suggestions I can give.
--
Mats

Don't forget to put break on each case, otherwise it will continue to the next one.