Re: enum and operator++

From:

Saeed Amrollahi <amrollahi.saeed@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Wed, 20 Jan 2010 07:57:59 -0800 (PST)

Message-ID:

<87d63a4b-5ff5-402a-ba52-4c9e69814254@34g2000yqp.googlegroups.com>

On Jan 20, 6:38 pm, REH <spamj...@stny.rr.com> wrote:

On Jan 20, 10:07 am, Saeed Amrollahi <amrollahi.sa...@gmail.com>
wrote:

Dear all
I am struggling with a problem that's simple per se.
I have an enum and a prefix ++ operator:
enum Dir { North = 1, East = 2, South = 3, West = 4, Max_ = 5=

}; //

clockwise

Dir operator++(Dir d)
{
  Dir dd;
  switch (d) {
  case North:
    dd = East;
    break;
  case East:
    dd = South;
    break;
  case South:
    dd = West;
    break;
  case West: // wrap
    dd = North;
    break;
  };

  return dd;

}

void f()
{
   for (Dir d = North; d < Max_; ++d)
    // do something

}

The problem is: in the above loop the ++ doesn't work,
indeed the loop is infinite. If you replace // do something with
output statement, it prints 1 forever.

Of course it's forever. Your comment says it all: West wrapped back to
North. You never hit Max.

Incidentally, you can write your operator much, much simpler than
using a case statement.

REH- Hide quoted text -

- Show quoted text -

Hi

You are right. My code had two problems. Yu found one of them
and you found the wraping one. I removed the wrap logic in switch
statement.

BTW, why I have to write
  d = ++d;
rather than
  ++d; ?

Thanks,
  -- Saeed