Actually, if I've presented the GRT as anything other than a refinement of the Schwartzian Transform then I've communicated myself poorly.

The whole reason I started by discussing the Schwartzian Transform in my original post was to explain GRT in the context of the Schwartzian Transform.

Personally I would call anything along these lines a Schwartzian Transform, but when it was warranted would instead use the more specific term GRT, but this is not in the slightest meant to imply that a GRT isn't a Schwartzian Transform. I suppose its like the square/rectangle idea. All GRTs are Schwartzian Transforms but not all Schwartzian Transforms are GRTs.

I would say that in the texts I've read (and your own snippet here in the monastery) Schwartzian Transforms are characterized by using an inorder function that accesses part of a wrapper containing the precomputed keys, whereas GRTs are characterized by not having an explicit inorder function at all.

I don't believe that the GRT can be sufficiently generalized in any practical sense to cover all problems, hence knowing both manifest map-sort-map strategies (and inventing others) is probably the best meta-strategy.

I couldnt agree more. (And stated something like this at the end of my post, although not in so many words)

Oh and thank you for introducing such an interesting technique to me and the community as a whole. I use it all the time.

PS - It would be really cool if you retitled your snippet Schwartzian Transform to "Schwartzian Transform (ST)" so that we could link to it via [ST] ;-) Or even write a new node explaining it a bit, you know straight from the horses mouth so to speak. But perhaps you dont have enough time?

Yves / DeMerphq
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When to use Prototypes?

I don't believe that the GRT can be sufficiently generalized in any practical sense to cover all problems

Easy. Imagine you have to sort objects. Objects written by someone who understands encapsulation (hence, unlikely to be a native Perl programmer). So, there's no way to compare two objects using an operator - you've got to call a method in one of the objects, passing the other as argument, for instance:

@sorted = sort {$a->cmp($b)} @unsorted;
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I doubt you can either use a ST or a GRT (I am one of the people who don't think GRT is a special case of ST) to sort this.