Alan Manuel Gloria:
> As an aside, one thing we *still* don't support very well is CL's
> loop. You're pretty much constrained to use parens for that to get
> any readability.
Miracle-working takes extra work :-). CL's loop is remarkably ugly in any
form. You're probably better off defining a sane macro that maps to the
underlying stuff than using it directly. Still, it might be instructive to
look at it.
Here's an example from Steele's "Common Lisp: The Language" 2nd ed, page 710:
(loop for i from 1 to (compute-top-value)
while (not (unacceptable i))
collect (square i)
do (format t "Working on ~D now" i)
when (evenp i)
do (format t "~D is a non-odd number" i)
finally (format t "About to exit!"))
You could just use (...) and handle it with modern-expressions. That's
probably what I'd do, since CL loops represent a particularly nasty case for
indentation processing:
(loop for i from 1 to compute-top-value()
while not(unacceptable(i))
collect square(i)
do format(t "Working on ~D now" i)
when evenp(i)
do format(t "~D is a non-odd number" i)
finally format(t "About to exit!"))
But we could try using indentation processing, using "~" as SPLIT and GROUP.
Here's my try; it's not beautiful, but it's not too bad considering what we're
trying to do:
loop for i from 1 to compute-top-value()
. while ~ not unacceptable(i)
. collect ~ square(i)
. do ~ format(t "Working on ~D now" i)
. when ~ evenp(i)
. ~ do ~ format(t "~D is a non-odd number" i)
. finally ~ format(t "About to exit!"))
I wouldn't want to design a notation just for CL loops; people point to that as
something "we never want to do again". But if there's a simple general
technique that solves many issues, then great.
Thoughts?
--- David A. Wheeler
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