Contract programming syntax

[Christopher Wright]

Denis Koroskin wrote:
> On Thu, 09 Apr 2009 00:51:49 +0400, Christopher Wright 
> <dhasenan at gmail.com> wrote:
> 
>> bearophile wrote:
>>> But isn't a syntax like the following better? To me it looks more 
>>> logic, because in{} and out(){} are part of the function, and there's 
>>> no need of a special syntax for the body (and the 'body' keyword):
>>>  long squareRoot(long x) {
>>>     in {
>>>         assert(x >= 0);
>>>     }
>>>      out (result) {
>>>         assert((result * result) <= x && (result+1) * (result+1) >= x);
>>>     }
>>>      return cast(long)std.math.sqrt(cast(real)x);
>>> }
>>
>> No. This proposed syntax change is quite misleading. Contracts cannot 
>> access the function's local variables, but it looks like they can. 
>> Contracts are executed at particular times, but that syntax makes them 
>> look like they execute wherever they are written.
>>
>> I believe you can put "body" before each function body, even with no 
>> contracts, if it makes you happier.
>>
>>> Bye,
>>> bearophile
> 
> Does scope(exit) also make you feel that it is executed immediately?

Well, take this example:

void foo(int i)
{
    if (i < 0) return;
    scope (exit) logExit;
}

The position has meaning here.

Then take this example:

void foo(int i)
{
    if (i < 0) return;
    in { assert (i != -1; }
}

This is confusing.

Good style dictates that your contracts should be separated from the 
body of your function, though.

The bigger issue is the apparent nesting of scopes.