Chavdar Botev wrote:
Peter Reilly wrote:
The original code may be slightly incorrect (my understanding
of java generics is not high).
Ha-ha. I think the original code cannot be slightly incorrect. It is
either correct or incorrect. ;) It certainly possible that my
understanding of Java generics is wrong. I come from a C++ templates
background and although syntactically similar, Java generics and C++
templates seem to be very different. C++ templates are just fancy
macros. Java generics are types. Unfortunately, I think that these
syntactic similarities can often lead to misconceptions and errors.
I dont fully understand generics.
They are only half way to full types, in ways that fail in interesting
ways.
Now, one aspect of C++ 2.0 templates is that they really are macros, so
bind at compile time to the types. This is why you can do very efficient
work with integers in STL, without needing boxing/unboxing. You cannot
do any runtime introspection, and all that stuff in C++ related to run
time typing is just wierd.
The problem with the project I posted is the inconsistent behavior. If
my code is incorrect, that's fine, I'll have to rework it. In this
case, the compilation should always fail. If the code is correct, the
compilation should always succeed.
Anyway, I think I am going to post on the Sun Java problems to try to
locate where the problem is. Is it in my possibly incorrect
understanding of Java generics, is it in the java compiler, or is it
in Ant which puts the destination directory in the classpath?
As of the previous comments about the value in using Java generics, I
think the biggest value is not saving some typing. In fact, with the
lack of typedefs, this saving is rather dubious. I think the biggest
advantage is that they allow the Java compiler to do a lot of type
checks at compilation time. In previous versions of Java, you could
add an Apple to a collection of Oranges and you will not know this
until you try to retrieve the Apple and type-cast it to an Orange.
Anything that avoids a runtime error by doing a compile-time check is
good in my book.
1. I dont like all the extra typing you need everywhere; it makes things
more verbose. What is wrong with polymorphic type inference?
2. its still trivially easy to add an orange to the hash table of
apples. The underlying hashmap/table is not protected.
3. there are some 'metatypes' I cannot write. Or they compile, but dont
work as expected.
This doesnt mean I am not enamoured of java5, its just generics are a
bit of a disappointment.
-steve
---------------------------------------------------------------------
To unsubscribe, e-mail: [EMAIL PROTECTED]
For additional commands, e-mail: [EMAIL PROTECTED]
