switch()

[Steven Schveighoffer]

On Wed, 19 Feb 2014 04:42:19 -0500, Daniel Murphy  
<yebbliesnospam at gmail.com> wrote:

>
> "Steven Schveighoffer"  wrote in message  
> news:op.xbhnw5rbeav7ka at stevens-macbook-pro.local...
>
>> It may not be mindless. Most people who want to handle the default case  
>> do it. It's usually not so much "I didn't think of handling other  
>> values," it's more "I never expect other values to come in, go away  
>> annoying compiler error."
>
> So why not put an assert(0) in instead of a break?  Tell the compiler  
> that you're assuming there are no other possible values.  This is  
> obviously the right thing to do here, and even if you ignore it the  
> compiler _is_ trying to help you.

Putting default: assert(0); changes the meaning of the code. In other  
words:

switch(x)
{
    case 1: ...
}

is the same as:

switch(x)
{
    case 1: ...
    default: break;
}

You are keeping the code the same. I don't think people would think of  
adding the assert(0), I wouldn't.

And as Ary pointed out, it may be that you expect the default to occur,  
but don't want to do anything.

>> I think it's the same as saying you have to always have an else clause  
>> after an if statement, even if it's "else {}"
>
> If 'if' was primarily used for the same thing that switch is, this would  
> be perfectly reasonable.

'if' and 'switch' are commonly used interchangeably. Frequently one uses  
'switch' where they would normally use 'if' to avoid evaluating something  
multiple times.

-Steve