Is ES3 good enough? Was incrementally strengthening ES3 paradigms considered?
dherman at ccs.neu.edu
Tue Nov 13 11:04:42 PST 2007
> Could the Scheme aspect of ES be strengthened? Tail recursion and let
> statements seem like good additions. What about macros? Please!
I can speak to the topic of macros. The group has been open to the
possibility of macros for a future version of ES, but not Edition 4.
There are not very many languages with non-Lisp syntax that have come
close to the power of Lisp/Scheme macros. CPP is distinctly *not* an
inspiration! :) Dylan may provide some inspiration, and possibly Boo and
Nemerle, though I have to learn more about these languages.
the popular view that parsing is a wholly solved problem in CS, moving
Lisp-style macros out of the domain of S-expressions and into
token-based syntaxes is far trickier than you might first suspect.
Hygiene is another important desideratum; scaling up C macros to be
closer to the power of Lisp macros means dealing with the kinds of bugs
that arise from name clashes[*]. Automatically hygienic systems
generally "do the right thing" but there are a number of different
algorithms to choose from, and as Brendan says the last word about
hygiene has not been written (this is in fact the topic of my
dissertation work). However, the theory doesn't have to be set in stone
for the practice to proceed, and there are plenty of excellent, working
Scheme implementations with fantastic macro systems that have been
around for many years. There's lots of good inspiration to draw from.
So the short answer to your question is: maybe, but not yet. :)
[*] These problems don't arise in standard C, but with e.g. the GCC
extensions to CPP you can easily cause these kinds of name capture.
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