Mastering Expression Evaluation in EmEditor: Clarifying Truth From Falsity for Enhanced Coding

Viewing 7 posts - 1 through 7 (of 7 total)

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• October 14, 2011 at 6:51 am #9732
  Stefan
  Participant
  How can i utilize this feature please?
  (?n:true_expression:false_expression)
  Found at:
  http://www.emeditor.com/modules/feature1/rewrite/tc_35.html
  EmEditor Professional 9 New Features
  The replace format “(?n:true_expression:false_expression)”
  was added to regular expression replace formats.
  October 17, 2011 at 8:10 pm #9741
  JohnQSmith
  Participant
  I played with it a while and finally figured it out. Here’s an example.
  Input document
  TheGreenAile TheGreenBile TheGreenCile TheGreenDile
  TheGreenEile TheGreenFile TheGreenGile TheGreenHile
  TheGreenIile TheGreenJile TheGreenKile TheGreenLile
  TheGreenNile TheGreenOile TheGreenPile TheGreenQile
  TheGreenRile TheGreenSile TheGreenUile TheGreenVile
  TheGreenWile TheGreenXile TheGreenYile TheGreenZile
  Search string
  (?:([BFNPR])|([^BFNPR]))(ile)
  Replace string
  (?1:M:T)3
  Replace all and output is
  TheGreenTile TheGreenMile TheGreenTile TheGreenTile
  TheGreenTile TheGreenMile TheGreenTile TheGreenTile
  TheGreenTile TheGreenTile TheGreenTile TheGreenTile
  TheGreenMile TheGreenTile TheGreenMile TheGreenTile
  TheGreenMile TheGreenTile TheGreenTile TheGreenTile
  TheGreenTile TheGreenTile TheGreenTile TheGreenTile
  I color coded it to help you see what’s happening.
  Oh yeah, the Boost regex docs helped me figure it out.
  October 18, 2011 at 5:46 am #9742
  Stefan
  Participant
  Thanks John!
  I see it, but i don’t understand it.
  Will have an closer look and read the Boost help…
  October 18, 2011 at 7:18 am #9743
  Stefan
  Participant
  > Conditionals
  > The character ‘?’ begins a conditional expression, the general form is:
  > ?Ntrue-expression:false-expression
  > where N is decimal digit.
  > If sub-expression N was matched, then true-expression is evaluated and sent to output,
  > otherwise false-expression is evaluated and sent to output.
  > You will normally need to surround a conditional-expression with parenthesis in order to prevent ambiguities.
  > For example, the format string “(?1foo:bar)” will replace each match found with “foo” if the sub-expression $1 was matched,
  > and with “bar” otherwise.
  > For sub-expressions with an index greater than 9, or for access to named sub-expressions use:
  > ?{INDEX}true-expression:false-expression
  > or
  > ?{NAME}true-expression:false-expression
  >
  > conditional expression ?Ntrue-expression:false-expression
  >
  > In addition, conditional expressions of the following form are recognized:
  > ?Ntrue-expression:false-expression
  > where N is a decimal digit representing a sub-match.
  > If the corresponding sub-match participated in the full match, then the substitution is true-expression.
  > Otherwise, it is false-expression. In this mode, you can use parens () for grouping.
  > If you want a literal paren, you must escape it as (.
  Seams clear, but i have still problems using this.
  Some tests:
  
  conditional expression
  ‘?Ntrue-expression:false-expression’ test 1
  
  I have:
  Test Price 1000
  Test Price 100
  Test Price 800

  Find: (.+) (.+) (d{3})(d)
  Replace: (?4: too expensive: affordable)
  [X] Use RegEx

  Result:
  Test Price 1000 too expensive
  Test Price 100
  Test Price 800

  Expected:
  Test Price 1000 too expensive
  Test Price 100 affordable
  Test Price 800 affordable

  Explanation:
  If sub-expression No. 4 match THEN
  use ‘true-expression’
  else ‘false-expression’
  
  conditional expression
  ‘?Ntrue-expression:false-expression’ test 2
  
  I have:
  Color 1 green
  Color 2 blue
  Color 3 red
  The available colors are either green, blue or red.

  Find: (Color d) (.+)
  Replace: (?1:1 2-ich:1 -2-)
  [X] Use RegEx

  Result:
  Color 1 green-ich
  Color 2 blue-ich
  Color 3 red-ich
  The available colors are either green, blue or red.

  Expected:
  Color 1 green-ich
  Color 2 blue-ich
  Color 3 red-ich
  The available colors are either -green-, -blue- or -red-.

  Explanation:
  Only if sub-expression No. 1 will match THEN
  use ‘true-expression’
  else ‘false-expression’
  OK, i will test some more.

October 18, 2011 at 2:39 pm #9744
JohnQSmith
Participant
I see the problem with both of your tests. It’s the same thing that took me so long to figure out how it works.
Here’s the key…
The whole RegEx must match in order for it to work. In other words, you have to set up the RegEx with an alternation so that it has both a success and a failure point.
In your first test, only the first line matched your RegEx (I’m using underscores as filler to demonstrate).

Test Price 100______0  
(.+) (.+)  (d{3}) (d)   <-- this matches  
    
Test Price 100________  
(.+) (.+)  (d{3}) (d)   <-- this doesn't match, there is no final (d)  
    
Test Price 800________  
(.+) (.+)  (d{3}) (d)   <-- also doesn't match  
 Here’s how I changed your RegEx to work.  

        Note the success ----.  and failure points  
                             |  |  
                             v  v  
Find: ^(.+) (.+) (d{3})(?:(d)|$)  
Replace:  (?4:too expensive:affordable)  

Your second example is the same thing.

Color_ 1__ green  
(Color d) (.+)   <-- match  
    
Color_ 2__ blue  
(Color d) (.+)   <-- match  
    
Color_ 3__ red  
(Color d) (.+)   <-- match  
    
The available colors are either green, blue or red.  
(Color d) (.+)   <-- no match anywhere on line  
 Hope this helps.  

October 18, 2011 at 6:12 pm #9745
Stefan
Participant
Thank you.
My understanding right now:
You have to set up the FIND RegEx with an alternation so that it has both a success and a failure point.
As the REPLACE have too possibilities too: (?n:true_expression:false_expression)
Test:

I have:  
Test Price 1000  
Test Price 100  
Test Price 800  
    
Find: (.+) (.+) (d{3})(d)*  
Repl: (?4: too expensive: affordable)  
[X] Use RegEx  
    
Result:  
Test Price 1000 too expensive  
Test Price 100 affordable  
Test Price 800 affordable  

Thanks again. I still have to do some test, but i think you showed me the way.
–
BTW, good idea :lol: of you:
Replace: (?4:too expensive:affordable)
–
October 18, 2011 at 6:39 pm #9746
JohnQSmith
Participant

My understanding right now:
You have to set up the FIND RegEx with an alternation so that it has both a success and a failure point.
As the REPLACE have too possibilities too: (?n:true_expression:false_expression)
Absolutely correct. I like your FIND RegEx better. It will be much easier to use than mine. Just adding the zero or more switch makes it much simpler than a non-matching alternation grouping.
What helped me the most in figuring out how it works was how EmEditor highlights all matches when you do a search. When I tried your first search, only the first “Test Price” line was highlighted, but when I removed the final “(d)”, all the lines were marked. This showed me that the problem was with the RegEx.
The first and foremost thing to remember is that the WHOLE RegEx expression must match before you can do any further matching and testing with a SUBexpression.
BTW, good idea :lol: of you:
Replace: (?4:too expensive:affordable)
Thanks! :-D

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