[Arjen Markus] (9 March 2005) I created this page to collect small code fragments about the various tricks you can use to process text. Most of the time these tricks do not merit a page of their own, but they do merit a place on the Wiki :).

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[AM] I had a problem with files that contain "continued lines". Here is a sketch:

    line with info \
          continued on the next line (see the backslash) \
          and the info is: Aha=BBBB
    another line with info - here the info is: Aha=CC

I needed to extract information from the complete lines. Now usually I read files line by line and analyse the lines one by one. You can not do that with this type of layout. Or can you? Here is my little trick:

   set contents [read $infile] 
   set contents [string map [list "\\\n" " "] $contents]
   foreach line [split $contents \n] {
      .. process the line ...
   }

This little fragment of code=:
   * reads the complete file (in my case they were not very large)
   * replaces the trailing backslash (and the newline) by a single space
   * splits the contents into separate lines again

No need to check if the line is complete or not - just use a few commands.
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[CLN] When you get the contents of a text widget, you get an extra trailing newline.  If you read the contents of a file, insert it in the widget, and just save those contents, you'll add a blank line at the end of the file for each save.  The solution is to save one less character than [[$text get 1.0 end]] returns, something like [[puts $fid [[string range [[$text get 1.0 end]] 0 end-1]]]].

[ECS]: Why not this: [[puts $fid [[$text get 1.0 end-1c]]]]?
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[schlenk] If a data file or text is already quite similar to a Tcl program one can sometimes easily map it to a Tcl program and just execute it. One Example for this:

A plotter data file like this:
 ;PU 640, 6900
 ;PD   640,  6909
 ,   640,  6913
 ,   640,  6917
 ,   640,  6921
 ,   640,  6924
 ;PU   641,  6928
 ;PD   641,  6932
 ,   642,  6936
 ,   643,  6940
 ,   644,  6944
 ,   645,  6947
 ,   646,  6951

Looks already quite similar to a Tcl program, we just need to reformat it a little bit.
This does the trick:

 set data [string map {  \n "" ; \n  , "" } $data]

Now we have to setup a nice evaluation environment, so we do not get surprised:
 
 proc dummy_unknown {args} {return}
 proc PD {args} { 
     foreach {x y} $args { puts "PenDown ( $x , $y )" }
 }
 proc PU {args} {
     foreach {x y} $args { puts "PenUp ( $x , $y )" }
 }
 set i [interp create -safe ]
 $i eval {namespace delete ::}
 interp alias $i unknown {} dummy_unknown
 interp alias $i PD {} PD
 interp alias $i PU {} PU
 
And at last just evaluate our little program:
 interp eval $i $data

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... next trick? ...

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[[
[Category Word and Text processing]
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