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Re^6: Understanding the Schwartzian transform.

by choroba (Chancellor)
on Jul 22, 2013 at 16:05 UTC ( #1045686=note: print w/replies, xml ) Need Help??

in reply to Re^5: Understanding the Schwartzian transform.
in thread Understanding the Schwartzian transform.

Because in GRT, you just change the data so they can be sorted lexicographically as strings, while in Schwartzian transform, you create a structure. You can simplify both to map {} sort {} map {} list (in GRT, sort block can be omitted), their difference can be seen only if you give more details.
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Re^7: Understanding the Schwartzian transform.
by Laurent_R (Abbot) on Jul 22, 2013 at 18:07 UTC

    Agreed, but: 1. the OP did not ask for the difference between Guttman-Rosler and Schwartzian transforms, but only if MJD's code he had was a canonical ST. And this example is a canonical ST, which it what I said. The fact that I somewhat summarized for brevity (and because it could be other code for a different probklem and still be a ST) does not invalidate my point and certainly does not make the OP's initial code nor the summary that I made a GR transform. As you said, a GR transform would have omitted the sort block. I reallyt think that the OP question was whether the standard ST consists of the map-sort-map construct.

      Agreed ... OPs question

      Yes, the original is canonical ST, there is no disputing that (you answered correctly)

      But your shortening (somewhat summarized for brevity ) to  @out = map {} sort {} map {} @in is definitely not the canonical Schwartzian Transform

      because the essence of ST is not the pipeline, pipeline is regular usage of map/grep, its even present in GRT. The essence of ST, the trick of it, the rule of it , [ is the caching ] .

      If you replace the essence with  {BLOCK} its unrecognizable, might as well call it  transform / sort / transform -- nothing Schwartzian about it :) and not very descriptive, unlike decorate-sort-undecorate which describes both ST and GRT

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