Thread: Cleaning up my code

Originally posted by bennyandthejets
I don't understand why it must be const.

It's just the design of the switch statement. Each case label must have a constant value. By restricting the cases to constant values, it allows the compiler to make more aggressive optimizations on the jump table.

Try this in your compiler:

Code:

#include <iostream>

using namespace std;

int main()
{
  int one = 1;
  int two = 2;

  int val = 1;

  switch(val)
  {
  case one: cout << "one" << endl; break;
  case two: cout << "two" << endl; break;
  }

  return 0;
}

I get the following errors:

$ g++ test.cpp
test.cpp: In function `int main()':
test.cpp:14: case label does not reduce to an integer constant
test.cpp:15: case label does not reduce to an integer constant

However, change it to this:

Code:

#include <iostream>

using namespace std;

int main()
{
  const int one = 1;
  const int two = 2;

  int val = 1;

  switch(val)
  {
  case one: cout << "one" << endl; break;
  case two: cout << "two" << endl; break;
  }

  return 0;
}

And it compiles without errors.