Re: [BLACKBOX] AW: [BLACKBOX] Modified DevSearch

From: [at]} <Alexander>
Date: Sat, 7 Feb 2009 00:37:50 +0600

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Hello!

ZH> I did not care about spaces highlighting or not. I forgot to mention that

ZH> red is wrong highlighting
ZH> blue is correct highlighting

ZH> In the first example the red word INC(n) is wrong highlighting
ZH> with your version and correct not highlighting with the original version.

  Unfortunately, whitespace sensitivity is exactly what matters in
  this case. The text comparison works as follows:
  1. you compare two texts character by character from a certain
  point, and while the characters match, you see there is no
  difference;
  2. once you found a mismatching pair of characters, you see that the
  texts are different, and you've found the start of the changed
  place;
  3. you need to find the end of the changed place. How to do it?
  DevSearch starts looking for a matching piece of text 32 characters
  long (see DevSearch.compMatchSize constant). Once such a piece is
  found, it thinks that the changed part ends before the matching
  piece and sets the highlighting according to the found boundaries.

  In the first code sample a space character after "INC(n)" was
  replaced with EOL character. The old DevSearch version did not
  distinguish the two, so it considered the "INC(n)" to be a part of
  non-modified stretch of text. My whitespace-sensitive version of
  DevSearch sees the difference, so the 32-character match is broken
  and must be sought for after the "INC(n)".

  If you set DevSearch.compMatchSize = Length("INC(n)") = 6, then you
  will see that the highlighting is "fixed". But you may then witness
  the mess it does with the second code sample comparison.

  Clearly, the default DevSearch.compMatchSize = 32 is an arbitrary
  number, and it is impossible to make it fit all cases: setting it
  too small will make it find many small differences where there is
  actually only one big, and setting it too big will make it unite
  several medium changes into a huge one.

  I can make whitespace sensitivity an option, e.g. exported as a
  BOOLEAN variable to be changed by tools like Josef Templ's custom
  Config module. The default setting could be the old behaviour.

ZH> The second sample is showing twice:
ZH> First one: the wrong combination of your version in red
ZH> Second one: the right combination of the original version in blue.

ZH> I hope that helps

  Indeed it does.

  The second sample is just another one of those "on the edge" cases,
  where whitespace consideration triggers the change. You see, the
  piece of text "THEN INC(i); j := (j + 1) MOD maxPat" (which is
  present both in the comment and after it) is 36 characters long if
  you COUNT space characters, and 28 if you DON'T. One of the numbers
  is above the DevSearch.compMatchSize limit, the other is below. That
  makes the difference, and shows how arbitrary the "32" value
  actually is.

---=====---
 Alexander

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Received on Fri Feb 06 2009 - 19:37:50 UTC