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.
this.myfirst = undefined;
this.myarray = [ ];
}
MyClass.prototype.mymethod = function (arg1, arg2) {
this.myfirst = arg1;
this.myarray.push(arg2);
};
This makes for some awkward javascript when converted directly into Parenscript because:
- The method
mymethod()will try to return the result ofArray.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 mysomething’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.
this.myarray.push is read in as one symbol, so if push is a macro, it won’t get macro expanded, and if myrarray is a symbol macro, it won’t be expanded either. That might be why your macros are not expanding, and why I made the “.” syntax unsupported (Parenscript should issue a warning every time it sees such a symbol). It’s possible to modify the readtable to treat “.” dots properly, but the dot character is already used for dotted lists in the standard CL readtable. I might provide that as an optional readtable that people can use with their code.
About CL-WHO, I just recommend going with straight HTML templates. It’s easier to work with and more flexible (you can have your templates writing out to a stream or returning strings in any way you want). And no more confusion about exactly what the output should look like. CL-Interpol actually makes a good solution: http://paste.lisp.org/display/118522
The only problem with that approach is that there is no mode for emacs that will indent HTML mixed with s-expression properly (yet).
I mentally discarded HTML-TEMPLATES off the top because I expect to have a bunch of DIV’s that have similar but not identical content and it just felt easier to do in Lisp than in TEMPLATE loops.
The CL-Interpol idea is interesting. I’ll keep that in mind.
Thanks.
One thing I have never had a good sense about is “what if my parenscript doesn’t work?” How do I debug parenscript-generated javascript? How do I patch it? Do I have to keep crashing my web app and starting over? Am I back to a variant of the old write-compile-test loop?
I know how to get a rudimentary REPL for developing in ordinary JavaScript — do I have to give it up to use Parenscript?
If you get this all figured out, give a talk about it at TC Lispers!
It seems possible to patch it through as a rudimentary REPL, but it would take a bit of work on both ends.
For my web application, I don’t expect it to be incredibly deep. So, the penalty for having to start over should be small. I suspect one of two things will happen:
Now accepting bets (or bribes).
Aw, heck. I’m already hooked. I’ll still take bribes, but it’s gonna be number 2.