Changing the Content-type just lets the browser know that you're using xhtml rather than html. This will occasionally cause some issues when using svg.arc in combination with html.arc because the browser will expect your html to be xhtml compliant. This could probably be smoothed over by creating an xhtml version of html.arc and modifying the generated code so that its xhtml compliant.
The server will need to specify arbitrary content-types eventually, and that's way easier than supporting xhtml, so specifying an arbitrary MIME type seems like the obvious solution to me. Also, the official MIME type for SVG is image/svg+xml, so trying to use xhtml both for SVG and HTML seems like a fragile hack.
Thanks for the great replies- I was actually also wondering how the RSS feed in news.arc deals with this... Is there some hack in there for overriding the Content-Type or are web browsers more forgiving for RSS feeds? I couldn't find any specific handling in news.arc for this issue on inspection the other day...
Firefox's Live HTTP Headers plugin tells me that news.ycombinator.com/rss has "Content-Type: text/html; charset=utf-8". I imagine RSS clients are not very strict about what they accept.
I'll also be there. I live in S.F. but I'll be spending Friday night close to campus at the Westin so I don't have to worry about getting there on time Saturday morning.
From what I've seen so far it looks like pg is staying away from using ? in predicates. In most cases it just makes the name longer. However, I saw this factorial function (rec zero 1 * 1-) in pg's Succinctness is Power essay and thought this (rec 0? 1 * -1) would be an interesting alternative. But then you lose the consistency of all your pedicates not having ?.
The question in my mind is "Why don't the extra character(s) justify the semantic implication?"
Yes, having to type ? or ! is an extra character, and over the course of large applications can add up to dozens of extra characters. Still, I'd argue that these extra characters are truly overshadowed by the language semantics that such characters would embody. One of Arc's goals is certainly to be an easy-to-learn Scheme implementation that people can "just use", and semantics of this sort are the kind that generally make the learning process smoother (at least in my own experience).
"Here again we are saved by our axiom that the user is a good programmer. We assume the user doesn't need operators to be called multiple-value-bind or invoke-restart-interactively to remember what they do."
That seems as clear a disagreement with your assertion as any.
Even if we accept this premise, it applies only to the core language and (de facto) standard libraries (for which we can assume familiarity). As soon as the language is defined in therms of it's implementation it also serves as a coding guideline and this is where the problem lies.
The difference between something like `multiple-value-bind` and `is?` -- especially in the given context -- isn't quite comparable to what Paul's speaking about there, I think. Adding an '?' to `is`, and an '!' to `map` is hardly at all comparable to making the function's name hideously long.
