switch case with dynamic

[lawrenced]

i am trying to use switch case with a variable and was wondering if some help could be offered

error I get is: error C2051: case expression not constant

I have the code:

for(int i = 0; i< vector1.end(); ++i)
  {
     int position = i;
     if(conditional)
     {break;
      }
      else{}
   }

switch(position)
 {
   case 0:
   case vector1.end() :
   default:
}

how can I achieve the above?

[anon]

Not possible with a switch. You may try if and else.

[Spidey]

error I get is: error C2051: case expression not constant

Yep, switch condition needs to be constant, vector.end() is not.
Also, your switch statement is outside you for loop so position is out of scope and cannot be seen by the switch statement.
Also, vector.end() returns an iterator so cannot be used in a for loop the way you are trying to.
I believe your looking for vector.size();

[Spidey]

Also, I dont know if you know this but you dont need braces after every if else statement, you can just do this -

if(conditional)
   break;
else
   ;

its just better looking.

[bithub]

If the else is empty, why have an else at all? Every if does not require a corresponding else.

[Spidey]

If the else is empty, why have an else at all? Every if does not require a corresponding else.

Yes, that is true as well.
Also, not sure if you left this out on purpose but every case needs a break as well otherwise it will fall through to the next one.

[Cooloorful]

Yes, that is true as well.
Also, not sure if you left this out on purpose but every case needs a break as well otherwise it will fall through to the next one.

That is actually the main feature you lose out on when you cannot use a switch/case. You can do something like this though.

namespace Case
{
  void moveup(void);
  void moveback(void);
  void moveleft(void);
  void moveright(void);
  void jump(void);
}

int position;

#define CASE(condition, action)  if (position == condition) { action } else
#define DEFAULT(action) action

int main(void)
{
  // code goes here...

  CASE(0, moveup(); jump();)
  CASE(vector1.end(), moveright();)
  DEFAULT(moveleft();movedown();)

  return 0;
}

Admittedly its not as intuitive to write, but it reads pretty clearly, yet uses a nasty global...

[Elysia]

It's even more nasty because it uses macros. I would get rid of them in favor of the "manual" way.

[Sebastiani]

That is actually the main feature you lose out on when you cannot use a switch/case. You can do something like this though.

namespace Case
{
  void moveup(void);
  void moveback(void);
  void moveleft(void);
  void moveright(void);
  void jump(void);
}

int position;

#define CASE(condition, action)  if (position == condition) { action } else
#define DEFAULT(action) action

int main(void)
{
  // code goes here...

  CASE(0, moveup(); jump();)
  CASE(vector1.end(), moveright();)
  DEFAULT(moveleft();movedown();)

  return 0;
}

Admittedly its not as intuitive to write, but it reads pretty clearly, yet uses a nasty global...

No, I would not recommend that approach at all.

[lawrenced]

many thanks for the help. it is enough to use if, else if , else statement