> A nice thing about the @[html] notation is that code colorizors
> will have an easier time colorizing the "def f():" properly.
> Another nice thing for us is that our spacing convention, of using
> no space between a function name and the parameters, can apply
> to all functions.

Interestingly, since using qpy, I now prefer the convention of having a
space between the function name and the parameters for _all_
function/method definitions and no equivalent space in the calls.

> Maybe @[xml] and @[str] should be our supported template decorators.

I'm perfectly fine with that.

> There is a pattern to follow, but there is no support at all for
> extending it.
> (Assuming that you want the kind of performance we enjoy with the
> current templates.)

Do you mean that for the possibility to add support for another quoting
category, in pure python, the implementation of the current categories
(xml, str) will need to necessarily become slower?

As for syntax, ok to leave the def fully py conformant, for colorizations
and other tool conveniences. But if the decorator variation is not really a
real py decorator, I'd still suggest it might be better to make that more
obvious, e.g doubling the @ seems to me visually more distinctive:

@@xml
def f (whatever):
  whatever

while still making the normal python compiler throw a syntax error.