• Yigal Chripun <yigal nowhere.home> Apr 27 2008

Max Samukha Wrote:

 On Fri, 25 Apr 2008 14:10:23 -0700, Walter Bright
 <newshound1 digitalmars.com> wrote:
 
Yigal Chripun wrote:
 BTW, what information does the compiler extract from an attribute?


With nothrow, for example, it can verify that the code inside the 
function cannot propagate an exception outside of it. I have no idea how 
you could do that with a user defined attribute.


 Like in .NET. And the proposed syntax was taken from C#. A number of
 intrinsic attributes are treated specially by the  IL compiler. For
 example, DllImport, Obsolete, MarshalAs, StructLayout etc. .NET has a
 nice extensible attribute system. User defined attributes can be
 inspected through reflection at run-time.  I guess, D could allow to
 do that at compile time as well. 


After some googling I've stumbled upon Nemerle which apparently already
implements most of my ideas. 
Nemerle is built on top of .net and has a bootstrapping compiler (the compiler
itself is written in Nemerle).
Nemerle provides many cool features including macros and attributes. From what
I understand, the way macros work is: you write a macro using their Compiler
APIs [1] and compile it, when you compile your program you also provide to the
compiler the compiled macro DLLs and the compiler uses them as "extensions" to
the compiler. This is very powerful and allows the user to even add his own
syntax to the language. Nemerle also provides CTFE and generics.

When I'll have more time, I'll read more about Nemerle and perhaps I'll write a
comparison. IMO, D has a lot to learn from Nemerle and Its IMO superior design
(based on what I've seen so far).

[1] http://nemerle.org/Class_library

-- Yigal