request switch statement with common block

[Borislav Kosharov]

On Monday, 5 August 2013 at 19:58:21 UTC, ron wrote:
> On Monday, 5 August 2013 at 08:46:54 UTC, Andre Artus wrote:
>> On Monday, 5 August 2013 at 06:28:12 UTC, luminousone wrote:
>>> perhaps a more generic solution should be looked at, extend 
>>> contracts to work with all scope blocks.
>>>
>>> switch(somenumber)
>>> in {
>>>   ... before stuff ...
>>> }
>>> out {
>>>   .... after stuff ...
>>> }
>>> body {
>>>   case 1:
>>>   in {
>>>      ... etc ....
>>>   }
>>>   out {
>>>      ... more etc ...
>>>   }
>>>   body {
>>>      ...
>>>   }
>>>   case 2:
>>>     // and so on
>>> }
>>>
>>> or perhaps
>>>
>>> for( int i = 0 ; i < 10 ; i ++ )
>>> in {
>>>   assert( i == 0 );
>>> }
>>> out {
>>>   assert( i == 9 );
>>> }
>>> body {
>>>  ... stuff ...
>>> }
>>>
>>> if it is desired for a particular contract block to be called 
>>> in release builds perhaps a attribute label to mark it as a 
>>> runtime block or something similar.
>>>
>>> foreach( i, k ; somerange )
>>> @runtime in {
>>> ...
>>> }
>>> body {
>>> }
>>
>> Please do not take offense, but I do not see this as a good 
>> idea. Contracts have a very different function; not just in D, 
>> but every language that uses them. The idea is to support 
>> design-by-contract programming. Overloading the constructs for 
>> the purposes proposed here would, in my opinion, cause 
>> confusion and/or weaken the proper use of contract programming.
>>
>>
>> The code in the contract conditions should never do anything 
>> more than what is necessary to specify the contract. It should 
>> not do explicit IO (other than implied by assert()), mutate 
>> state, or anything like that.
>>
>> At the bottom of this page you can find a reading list for 
>> more info.
>> http://www.digitalmars.com/d/dbc.html
>>
>> Or for a general overview:
>> http://en.wikipedia.org/wiki/Design_by_contract
>>
>> Walter, does the D compiler or any of it's companion tools do 
>> any static analysis on the contracts? Such as a void 
>> safety/null reference check?
>
> None taken, =-p.
>
> I don't see how this is different from current contract usage, 
> right now they apply to function scopes only. currently I 
> believe you could get a similar effect via using an inner 
> function.
>
> void a() {
>    int i = 0;
>    void b()
>    in {
>       assert( i == 0 );
>    }
>    out {
>       assert( i == 10 );
>    }
>    body {
>       for( ; i < 10 ; i ++ ) {
>          ... do something ...
>       }
>    }
>    b();
> }

Speaking of contracts, and reading the docs I see:
"Pre and Post Contracts

The pre contracts specify the preconditions before a statement is 
executed. The most typical use of this would be in validating the 
parameters to a function. The post contracts validate the result 
of the statement. The most typical use of this would be in 
validating the return value of a function and of any side effects 
it has..."

So are contracts possible outside function declarations? For 
example just scopes or random places in code.