On 2012-05-27 22:15, F i L wrote:
I'm not sure I follow all the details of what Andrei's suggesting and what's being talked about here, this parser/lexer stuff is still very new to me, so this may be a bit off-topic. However, I thought I'd weigh in on something I was very impressed with about the Nimrod language's direct AST access/manipulation.Nim has a "template" which is very much like D's mixin templates, example: # Nim template foo(b:string) = var bar = b block main: foo("test") assert(bar == "test") and the equivalent in... // D mixin template foo(string b) { auto bar = b; } void main() { mixin foo("test"); assert(bar == "test"); } which is all very straight forward stuff, the cool part comes with Nim's macro's. Nim has a two unique types: expr & stmt (expression & statement). They're direct AST structures which can be passed to template/macro procedures and arbitrarily mutated. Example: macro foo(s:stmt): stmt = result = newNimNode(nnkStmtList) for i in 1 .. s.len-1: var str = s[i].toStrLit() result.add(newCall("echo", str)) block main: foo: bar baz the above code prints: " bar baz " **Some notes: result is what's returned, and the reason you can use "foo" with a statement body is because any macro/template who's last parameter is type 'stmt' can be called with block semantics; similar to how UFCS works with the first parameter.** The above *might* look like the following in D: macro foo(ASTNode[] stmts...) { ASTNode[] result; foreach (s; stmts) { auto str = s.toASTString(); result ~= new ASTCall!"writeln"(str); } return result; } void main() { foo { bar; baz; } } This kind of direct AST manipulation + body semantics opens the doors for a lot of cool things. If you read through Nim's lib documentation you'll notice many of the "language" features are actually just Library procedures in the defaultly included system module. Which is great because contributions to the *language* can be made very easily. Also, the infrastructure to read/write AST is no-doubt immensely useful for IDE support and other such dev tools. I'm not a huge fan of everything in Nimrod, but this is something they definitely got right, and I think D could gain from their experience.
This is a very cool feature of Nimrod. It allows to move several language features to the library.
* synchronized * scope * foreach (possibly) -- /Jacob Carlborg
