Re: [Jython-users] Jython documentation

[Alexander S. <ast...@ma...>]

On Jan 22, 2007, at 11:11 AM, Diez B. Roggisch wrote:

>> I was thinking specifically of the case of interacting with existing
>> java libraries. Java methods still demand correct typing when used
>>
>> from jython. You get errors when doing things like:
>>>>> d = java.util.Date("'100")
>>
>> And the same would be true for methods on any java classes one has
>> written. However misusing a java generic will give no such error. So
>> you may get a deferred type error in java code which a java
>> programmer would think has been prevented by specifying the generic.
>>
>> So the issue isn't  the lack of type safety in jython, which I agree
>> is generally a gain, but the "odd" behavior of generic typing in java
>> code called from jython. Without thinking carefully about it one
>> might start looking for bugs in the wrong places.
>
> I see what you mean. However, the type errors are thrown by the JVM  
> - which
> isn't the case for generics, where it doesn't do anything because  
> of the type
> erasure.
>
> So I still find it odd to add typechecking in jython. Especially  
> since the
> latent classcast-exceptions that can result from it are known for  
> ages in
> java-development. Sure, generics can remedy that to a certain  
> extent - but
> just compile-time. One has to deal with runtime errors in jython  
> anyway, as
> they are the only thing (besides syntax errors) you get.
>
> And the added typecheck doesn't come for free, either. And things  
> can get ugly
> pretty fast, as in java I often have generics as parameters of  
> generics...
> So, when creating instances of java collections for e.g.
>
> Map<String, Map<Foo, Bar>>
>
> like this:
>
> my_map['key'] = {Foo() : Bar()}
>
> one has to ensure that the jython dict is properly type  
> annotated... Something
> I'm not even sure it can be done.
>
> nope. still not convinced ;)
>
> Diez

I'm not  proposing adding type checking,  just adding a note to the  
jython docs to remind folks that generics are completely invisible to  
jython and the JVM.

Alex