Thread: case of or

why can't you jump to a "x OR y"? in this case?

Code:

var
  I : Integer;
begin
  I := 0;
  case I of
    0 OR 1: MessageBox(0, '0 OR 1', 'info', 0);//why doesn't this work?
    else MessageBox(0, 'Will fail :)', 'info', 0);
end;

explain the first problem before continuing, please.
I also noticed strange behavior while fucking around, can anyone explain?

Code:

var
  I : Integer;
begin
 I := 0 OR 1;
  case I of
    0 OR 1: MessageBox(0, '"I := 0 OR 1;" ?)', 'info', 0);
    else MessageBox(0, 'Should Not Fail.', 'info', 0);
  end;
End

Code:

var
  I : Integer;
begin
  I := 0;
  case I of
    0..1: MessageBox(0, '0..1', 'info', 0);
    else MessageBox(0, 'Should Not Fail.', 'info', 0);
  end;
End;

Code:

var
  I : Integer;
begin
  I := 0 OR 1;
  case I of
    0..1: MessageBox(0, 'I := 0 or 1; 0..1 (also works with 0, 1):', 'info', 0);
    else MessageBox(0, 'Should Not Fail.', 'info', 0);
  end;

Code:

var
  I : Integer;
begin
  I := 0;
  case I of
    0, 1: MessageBox(0, '0, 1 (comma wtf?)', 'info', 0);
    else MessageBox(0, 'Should Not Fail.', 'info', 0);
  end;
End;

The problem with 0 or 1 is, that you can only have ordinal-values as "case"-values. So "0 or 1" in the case-statement is a binary operation, which has the result of 1. So it would only work if you set i to 1 (or to "0 or 1", which is equal 1).
When you set i:=0 or 1, i is 1, because it's a binary operation too. So the value stored in i is 1.
Hope this helps a bit.

ah! perfect explanation.

ASM explanation:
A switch is implemented like that

Code:

lea eax, [i * 4 + 0x12345678]
jmp eax

Now at 0x1245678 there would be the address of the code for the first case.
At 0x124567C there would be the address of the code for the second case.
At 0x1245680 ...