On Sunday, 21 April 2013 at 07:57:51 UTC, Suminda Dharmasena
wrote:
Hi,
Since macro is reserved perhaps D can introduce AST
manipulating macros.
Suminda
Hi!
As far as I can remember, macros have been deferred to D3 because
it has mixins and templates, so one can easily manipulate code in
D. However, it's been long time since there was serious
discussion about the implementation details. I'm happy to see
that the topic emerged again just before DConf - maybe the
discussion will continue there.
Several non-lispy languages introduced macros long ago so the
developers may learn from others mistakes and they will avoid the
pitfalls. These languages include Groovy,
Scala, Nimrod and Rust.
The Rust implementation is much like text substituation when
used, so one can easily learn it in an hour. Its syntax is a
little distinct from the base language, and there has been a
problem with lexing it according to a past issue:
https://github.com/mozilla/rust/issues/2755
It's still unfinished, there are some limitations. ( although
it's been always hard to debug them ) Have a look at:
http://static.rust-lang.org/doc/0.6/tutorial-macros.html
and also see the language manual ( at http://rust-lang.org )
Beyond AST macros, Nimrod ( http://nimrod-code.org ) has text
substituation mechanisms called templates - much like C macros or
templates in C++ and D. It also has term rewriting macros. In my
opinion, Nimrod is a language where a lot of features can produce
dirty code ( although some of them are very well done and they
are extremely powerful tools ), and it's the developer's choice
to use the features for the right purposes ( especially true with
term rewriting ).
So obfuscation is just as easy in that language as in C++ or
Perls before version 6 despite the fact that its sysntax is
derived from Python.
I can't say much about Scala and Groovy, but their syntax for
defining macros doesn't use as cryptic symbols as Nimrod. For
example I couldn't find out for first time what is nnk the nnk
prefix in the nnkInfix symbol.
Zsombor
