think about what "gibberish" you want it to expand to
Just to clarify, the gibberish I was referring to was the (sbcl-specific) backq-comma call. It's not gibberish if I know what I want :)
Update: Oh, you're talking about stepping through the code. Yeah, I should just not be lazy and do that. I'm again reminded of that dijkstra comment from yesterday. My mental code simulation skill have atrophied with programming experience. Then again, Dijkstra hated how schools taught their students to step through code pretending to be the computer. Hence his more axiomatic approach to program semantics.
Hmm, I wonder if fallintothis's macro stepping utility would help with this..
Update 2: Ok, digested. You make a lot of sense. It's too bad, already the solution's starting to crystallize in my head as self-evident, and I'm forgetting what it was like to not know how to do this. Your clear comment is not helping :p
The idea that any helper macro would also need nested backquotes is interesting and explains vague memories of past experiences. I'm going to think about that.
Part of the problem is that I've needed nested backticks so infrequently. Perhaps I should just create some contrived examples to exercise this muscle.
Just to clarify, the gibberish I was referring to was the (sbcl-specific) backq-comma call. It's not gibberish if I know what I want :)
Ah, gotcha. ^_^ I thought that was part of it, but I thought maybe you also meant things like the (list) with no arguments and the (progn ...) with one subexpression. I dunno, I sorta consider that to be gibberish even if we want it. XD
Oh, you're talking about stepping the code.
I guess I am.... Maybe some debug printing would help out. ^^
Actually, maybe something like debug printing is a good way to do unit tests on macros. O_o Put in a meaningless form inside the macro, and have it short-circuit with an escape continuation (or call any other kind of function) if the right test is in progress. You get to verify, collect, or trace intermediate values without managing a spaghetti of one-use functions.
In its simplest form, this could be implemented as a global variable that's usually set to 'idfn.
It's too bad, already the solution's starting to crystallize in my head as self-evident, and I'm forgetting what it was like to not know how to do this.
I was actually really afraid of that. XP Maybe a good reason will dawn on one of us after a while.
Part of the problem is that I've needed nested backticks so infrequently. Perhaps I should just create some contrived examples to exercise this muscle.
The clearest uses of quasiquotation in Arc are 'eval, 'defset, and 'mac. As long as you need to combine two or three of those things, look out. :-p
My trickiest quasiquotation experience was when I wanted (= global!x 2) to effectively do (eval `(= ,'x ,2)) somehow. I forgot that we could actually embed arbitrary values directly into Arc expressions, so I decided to use a temporary global variable and go for (eval `(= ,'x temp)). For encapsulation's sake, I made the global variable a gensym, which meant I had to (eval ...) the whole (defset ...) form. Three layers, and I'm not sure a macro would help.
Once rntz pointed out that I didn't need the temporary variable (http://arclanguage.org/item?id=11612), I changed it to use two layers. But maybe it's still okay as a contrived example. ^_^
I wonder if quasiquotation layers are something that intrinsically come up infrequently, or if it just has to do with the way 'eval, 'defset, and 'mac come up infrequently. In fact, the reason I defined (= global!x 2) was so that I didn't have to mess with a bunch of quasiquotes each time I wanted to jump up to global scope using 'eval, so my most extreme usage of quasiquotes was a tool to make quasiquotes less frequent.
That example's probably an exception though. I just realized that making a helper macro to remove a layer of quasiquotes is a bit futile because it has to wrap both the root of the quoted code and the missing leaves, essentially becoming another quasiquote. (It could be I'm just not being creative enough.) If the macro abstracts away two layers of quasiquotes, it might be worthwhile, but again, it'll either have all the same "tricks" as two-layered quasiquotes or be restrictive and less general-purpose.
