JoostVisser and I have looked at a breadth first for
Tools.JJTraveler. The breadth first in the Stratego library
is incorrect:
- It doesn't apply s to the root (and hence not to any node);
- It's not overall breadht-first, only breadth-first per node.
--
ArieVanDeursen; 25 Nov 2001.
It is indeed not a correct implementation of breadth first, but it does actually apply
transformations. Consider the definition:
breadth-first(s) =
rec x(all(s); all(x))
This first applies
s to all direct subterms of the root, and then recursively applies
x to
the direct sub-terms. The difference with topdown is that all subterms are visited, before
visiting subterms recursively. What is a better name for this strategy?
kids-first maybe?
An implementation of proper breadth-first should employ a global queue data structure to which
terms to be visited should be added. It is also interesting to consider using
TermAnnotations to
let a term point to the next term in a breadth-first traversal.
--
EelcoVisser - 09 Dec 2001
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