Pluggable type sytems

[Denis Koroskin]

On Mon, 19 Jan 2009 16:26:47 +0300, Michel Fortin <michel.fortin at michelf.com> wrote:

> On 2009-01-18 21:29:02 -0500, bearophile <bearophileHUGS at lycos.com> said:
>
>> I think pluggable type systems will become more common in the following  
>> years (see also the optional annotations of Python3 that are designed  
>> for that too). This is more or less related:
>>  http://bartoszmilewski.wordpress.com/2009/01/18/java-pluggable-types/
>
> Nice post.
>
>> (but nonnullability is so basic that it's better inside the language,  
>> and not left out to a plug-in type system).
>
> I agree for non-nullability.
>
> In fact, I'd even argue that non-nullability should be the default for  
> pointers and class references, because it is either safer (if the  
> compiler doesn't do the null check for you) or less troublesome to use  
> (if the compiler forces you to check for null everytime). Another reason  
> being consistency: value-types can't be null by default and so should be  
> class references and pointers. And making pointers non-nullable by  
> default can only be done at the language level, so obviously it's better  
> in the language than as a user-defined type modifier.
>

Agree.