HTML + JS + LISP. Oh My. March 20th, 2012
Patrick Stein

I started a Javascript + HTML application some time back. I decided that I wanted to get some Lisp on. So, it was time to pull out Hunchentoot, CL-WHO, and Parenscript.

It’s been awkward slogging so far. I still don’t have a good user-model of when exactly I need to wrap something in a (cl-who:str ...) or when Parenscript will expand my macro rather than convert it into a function call or how I managed to get the cl-who:*attribute-quote-char* to finally stick for a few REPLs.

The other half of the awkwardness is that I started writing the application in idiomatic javascript with prototype-based objects.

function MyClass () {
  this.myfirst = undefined;
  this.myarray = [ ];

MyClass.prototype.mymethod = function (arg1, arg2) {
  this.myfirst = arg1;

This makes for some awkward javascript when converted directly into Parenscript because:

  • The method mymethod() will try to return the result of Array.push() (which, technically, is fine, but not really the intent of the method).
  • Almost every statement on the Lisp side ends up wrapping just about everything in (parenscript:chain ...). (Edit: Of course, I discovered right after posting this that the dot is left untouched in the Parenscript symbol conversion, so I can do (this.myarray.push arg2) instead of (parenscript:chain this my array (push arg2)). I’m certainly pleased with the brevity, but it pegs my something’s fishy here, Batman meter.)
  • I have an aversion to using any package other than COMMON-LISP, so everything is way clunkier than all of the tutorials and examples online.

I think that I’m going to scratch all of the Javascript and Parenscript code that I have right now and start over with a mindset of How would I do this if it were just in Lisp? Now, what extra hoops do I need to get Parenscript to make usable Javascript? rather than How would I do this in Javascript? Oh, and then, how can I make Parenscript say exactly that? And, I may bite the bullet and (use-package ...) both CL-WHO and Parenscript.

My Favorite Macro Patterns February 17th, 2012
Patrick Stein

I read Jorge Tavares’s article on Macro Patterns a few days ago.  I was thinking about replying to mention a few of my favorites:

  • The with- pattern which makes sure a special variable is bound for the body and makes sure the tied resources are released at the end of the block.
  • Macros which collect content (usually into a special variable) so they can do something with the content at the end of the close of the macro.

Then, I was working on something tonight when I re-discovered a favorite pattern that I’d forgotten about: Putting multiple wrappers on the same body.

I am working on an HTML+JavaScript+CSS project. In the end, I need static files. But, I thought I would use the opportunity to really experience CL-Who, Parenscript, and CSS-Lite.

I have now made a macro called define-web-file which takes a CL-Who or Parenscript body and wraps it up as both a Hunchentoot handler and a write-to-file wrapper. Now, I can test interactively with Hunchentoot and generate the whole web application when I’m ready.