Better Flow Control

01 Feb 2008

Been poking around the Arc site; I did a quick Vim integration (to allow sending files/forms to the running Arc process), and I’ve been reading its code a little, mostly to get a better understanding of the approach it’s taking for html generation.

There’s bad and good, but it’s certainly very terse. Here’s the Arc version of prompt, interstitial, and results:

(defop said req
    (aform [w/link (pr "you said: " (arg _ "foo"))
            (pr "click here")]
            (input "foo")
                  (submit)))

I’d written a Python library that makes things pretty terse (there’s an example on that page), but after seeing the Arc version, I wanted to trim it down some more. It now looks like:

@op
def said(req):
    def result(foo):
        cede(link("you said: " + foo,
                  "click here"))
    cede(aform(result, input("foo")))

There’s a bit of magic going on, but it’s quite nice and tidy I think. Compared to the Arc version, I prefer having foo as a regular argument to the handler function vs (arg _ foo) in Arc, but the simpler closures in Arc allow you to avoid cede and the name result which is a little nicer. It’s pretty close to a direct translation which I find interesting. I’ll definitely be keeping an eye on Arc as it develops, I found this an expanding experience.

h4ck3r.net

Better Flow Control