Greetings.
Quoting Asumu quoting Matthias:
I'd like to propose that there are three disciplined uses of macros:
1. data sublanguages: I can write simple looking expressions and
[...]
2. binding constructs: I can introduce new binding constructs with
[...]
3. evaluation reordering: I can introduce constructs that
delay/postpone
[...]
[Note: In Haskell, you don't need that one.]
This is a seriously naive question, because I have only trivial
experience with Haskell (and by extension other lazy languages), but
aren't each of these things that you can do with a lazy language?
If I can control when an expression is evaluated, then I can obviously
do (3), but supposing I can also control the environment within which
it's evaluated, can't I also do (2) and thence, with suitable juggling,
go on to (1)? Asumu's further example of 'use of macros that expand
into submodules in order to provide metadata for other programs/tools'
sounds at least complicated to do lazily, without macros, but not
fundamentally impossible.
Macros are obviously not the same as lazy evaluation (though from the
point of view of the macro expander, perhaps all the post-compilation
stages are 'lazy'), but I'm having a hard time seeing why it's obvious
they're not isomorphic.
I imagine there may be both pragmatic and fundamental semantic reasons
why the two are different.
All the best,
Norman
--
Norman Gray : https://nxg.me.uk
SUPA School of Physics and Astronomy, University of Glasgow, UK
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