why does the switch construct does'nt allows negative values to be used inside a case

[radha gogia]

I just wanted to ask the reason that why is the below code not checking the case -1 while working for the other case values.
#include<stdio.h>
#include<conio.h>
int main()
{
int i=-1;
switch(i-2)
{
case -1:printf("feeling fish");
break;
case 0:printf("heloo");
case 1:printf("mend ur ways");
default:printf("u r crect");

}
getch();
return 0;
}

So why in the below code the case -1 doesnt run,when the value evaluated by the switch construct is actually a negative integer constant.

[weaknessforcats]

The switch does work on negative values:

switch (-1)
{
   case -1:
     etc...
}

However:

int i = -1;
switch (i-2)
{
    case -1:
     etc...

won't go to case -1 because i-2 is not -1. i-2 is an expression which can be only true or false. You need the negative value to be in an integer variable.