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Wed Jun 25 19:34:45 CEST 2008

Automatic instantiation

from the blog post, which will probably be edited once i find a way to
express this properly (and solve the problem maybe..)

  Now, that's a nice story, but that's not how it happened :) The
  specification of rewriting rules came natural as a syntactic
  abstraction for some previously manually coded peephole
  optimizations. This rewrite system however seemed way more useful
  than just for performing simple optimizations, and by introducing
  pseudo target assembly instructions has been transformed into a
  different kind of two-level language semantics: powerful compile
  time type system with an analogous run time type system with
  'projected semantics' derived from eager macro rewrite rules.

  The downside of this is that in order to write programs, one has to
  make decisions about what to instantiate, and what not. It might be
  interesting to try how far this can be automated: don't instantiate
  what cannot be instantiated, but try to isolate subprograms that
  have real semantics.

Two things:

  Q: macro semantics and target semantics are not the same for some
     words like '+'. is this good or bad? it's useful for computing
     constants, but dangerous for overflows. is it better to
     completely embed the target semantics, and use different symbols
     for the metaprogramming operations?

  Q: is automatic instantiation really that difficult?


compile time + might be seen as a different type.. (like + and +. in
ocaml)

except for optimality (inlining might sometimes be better), solving
the instantiation problem based purely on semantics (inline when a
composition is 'real' + doesn't mess with the target interpreter)
might not be so difficult.



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