zlacker

>>pg+(OP)
Better display of source code in comments

>>vegash+0i
You can now include code in comments:

 (def codetree (file)
   (trav + 1 (readall (infile file))))

Anything that appears after two newlines and a blank space is treated as code, till there's a line that doesn't begin with a space. This is like the markdown convention, but you don't have to use four spaces; one will do.

Incidentally, the code above tells me the number of nodes in the code tree of a file. Not just leaves, which would be

 (len (flat (readall (infile file))))

but interior nodes as well. To me this is the best measure of how long a program is. I used to go by lines of code

 (def codelines (file)
   (w/infile in file 
     (summing test
       (whilet line (readline in)
         (test (aand (find nonwhite line) (isnt it #\;)))))))

but I found this was encouraging me to do the wrong things.

(This kind of test matters because I'm constantly trying to make news.yc shorter as a way of pushing functionality down into Arc.)

Here's trav, btw:

 (def trav (f base tree)
   (if (atom tree)
       (base tree)
       (f (trav f base (car tree)) (trav f base (cdr tree)))))

It traverses a tree, doing something at every node. So e.g. CL copy-tree would be

 (def copy-tree (tree) (trav cons (fn (x) x) tree))

If you're wondering how the second argument to trav in codetree could be 1, it's because a constant when called as a function simply returns itself. This turns out to be quite handy.

>>pg+Dq8
Stupid questions alert. ____________________________

In On Lisp, you mentioned that implementing continuations with closures via transformation to CPS could be accomplished by writing a code walker, but that this would be a "serious undertaking" in Common Lisp.

This struck me at the time and ever since as painful, but understandable. Macros aren't first-class objects in CL, so the code you're walking through could be very complex due to macro-expansion, and I could be wrong, but I don't remember if the resulting code would necessarily contain clues that tell us what macro generated it, etc.

Could one assume (and it is definitely an assumption, or speculation, not a deduction from what you've given us here!) that it would be much simpler in Arc? Say, a page or so of code?

>>mr_luc+7s8
I could make it as easy as I wanted to write a codewalker, by changing the language where necessary. But it's not a priority right now. I haven't been doing anything where I felt I needed a codewalker.