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Re: outdated m4sugar

From: Eric Blake
Subject: Re: outdated m4sugar
Date: Tue, 05 Aug 2008 06:27:06 -0600
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According to Akim Demaille on 7/24/2008 9:35 AM:
| But I guess that in the case of Bison, most of the cost is really in
| the "runtime" part, not the "load it all" part.  Yet it would be
| interesting to make a try.  I'll see if I can try that.

I think a big part of the "runtime" cost of bison would be the fact that
much of older m4sugar is quadratic rather than linear on m4 1.4.x (in
particular, these heavy hitters: m4_join, m4_foreach, m4_map, m4_shiftn,
m4_append).  For autoconf 2.63, all but m4_append have been made linear on
m4 1.4.x (you need m4 1.6 to make m4_append linear), and m4_append_uniq
has been augmented by the addition of m4_set_* which can be used in a
similar manner but in linear time.  All the more incentive for me to
continue work on porting newer m4sugar to bison.  In fact, I'm hoping that
some of the grammars in tests/torture.at are made tractable on larger
input sizes while completing in less time and memory once you switch to
linear algorithms in m4sugar.

- --
Don't work too hard, make some time for fun as well!

Eric Blake             address@hidden
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