On Fri, 2006-11-03 at 18:07 -0800, Dan Weston wrote:
Here's an idea that (I think) is useful and backwards compatible: fractional and negative fixity.
There have been 3 separate times where I've wanted an operator just above 0 ($) but less than 1 (>>= or >>>), or else just below 0 (like a superlow $$)
infix 0.5 ??? infix -1 $$
The only change would be internal to compiler, wouldn't it? Since fixity is just syntactic sugar, there should be no semantic difficulties.
I like it! One caveat: the grammar from the Haskell Report specifies a fixed number of precedence levels; if anybody has a Haskell parser implemented by feeding this grammar into a parser generator, they would have to rewrite the parser to implement this. (But it's quite possible that nobody has such a parser; the alternate approach of using a first pass that ignores precedences and fixing them up with a second-pass hand-written operator precedence parser seems to be easier and more popular, and should be easy to adapt to new precedence levels.) Carl Witty