Article on code features in C++ by Scott Meyers + sidebar on D implementation by Bartosz Milewski

[Lionello Lunesu]

"Walter Bright" <newshound1 at digitalmars.com> wrote in message 
news:gbjqan$2lh0$1 at digitalmars.com...
> Lionello Lunesu wrote:
>> Very cool, and very useful.. I really wish D would support 'features' 
>> natively. nothrow, pure, they all share the same behaviour: nothrow 
>> function can only call other functions with nothrow; pure function can 
>> only call functions with pure.. etc... Can't this be generalized?
>
> Both pure and nothrow are deeply embedded into the semantic analysis. I 
> don't see any way to generalize it. For example,
>
>  void foo() nothrow
>  {
>     try
>     {
>           throw new Bar;
>     }
>     catch (Object o)
>     {
>     }
>  }
>
> is valid code, while:
>
>
>  void foo() nothrow
>  {
>     throw new Bar;
>  }
>
> should issue a compile time error.

Is see your point.

Isn't that similar, though, to the functionality of "Relaxing feature 
constraints" from Scott Meyer's paper? The try-catch-scope can be considered 
"nothrow" because it can be called from other nothrow code. But inside the 
try-catch scope the constraint is relaxed and not-nothrow code (code that 
can throw) is accepted. I know next to nothing about compilers' inner 
workings, but it sounds like a small rule could be attached to try scopes.

L.