Re: possible bugs in Exegesis 5 code for matching patterns

[Smylers]

Steve Tolkin wrote:

   { $appendline =~ s/in_marker//;
 
 I think this needs a backslash in front of the  symbol, and a space
 after in_marker, i.e. it should be: 
 
   { $appendline =~ s/in_marker/\sp/;

Isn't the replacement part of a substitution is still a string?
Having the replacement being a rule would mean that you could write
things like:

  s:e/ \* / [aeiou] /;

That would replace asterisks with 'any' vowel, without specifying which
vowel to use.  That makes no sense at all.  (Well, not unless it creates
a superposition, but surely Damian can't have intended to introduce
superpositions like this is the core language?  Can he?)

So since pointy brackets aren't special in strings, it doesn't take a
backslash; similarly spaces should just be written as spaces.

 rule fileinfo {
 out_marker3 $oldfile:=(\S+) $olddate:=[\h* (\N+?) \h*?] \n
 in_marker3  $newfile:=(\S+) $newdate:=[\h* (\N+?) \h*?] \n
 }
 
 rule out_marker { \+ sp }
 rule in_marker  {  - sp }
 
 The sp means a single literal space.  So I think out_marker3
 means look for + + +  rather than +++ which is what is really
 needed to match a Unified diff.

Yes, you look to be right to me.

 If these are bugs, then what would be the best way to
 fix the code while retaining as much reuse as possible.

This is one way:

  rule out_marker_symbol { \+ }
  rule in_marker_symbol  {  - }

  rule out_marker { out_marker_symbol sp }
  rule in_marker  { in_marker_symbol  sp }

  rule fileinfo {
  out_marker_symbol3 $oldfile:=(\S+) $olddate:=[\h* (\N+?) \h*?] \n
  in_marker_symbol3  $newfile:=(\S+) $newdate:=[\h* (\N+?) \h*?] \n
  }

[While we're on the subject of typos, it looks like the final definition
of Cfileinfo in the exegesis has C$newfile where C$oldfile is
meant.]

But it'd probably be easier just to do:

  rule fileinfo {
  \+\+\+ $oldfile:=(\S+) $olddate:=[\h* (\N+?) \h*?] \n
  ---$newfile:=(\S+) $newdate:=[\h* (\N+?) \h*?] \n
  }

That isn't a terrible cop out to repeat the symbols, since there's no
reason why the format has to use the same symbols in both places.

Smylers

possible bugs in Exegesis 5 code for matching patterns

[Tolkin, Steve]

Here is a discussion thread of Exegesis 5 
http://www.perl.com/pub/a/2002/08/22/exegesis5.html at
http://developers.slashdot.org/developers/02/08/23/1232230.shtml?tid=145
But the signal/noise is too low, with side tracks into
Monty Python etc.   

In section Smarter alternatives there is this code:
{ @$appendline =~ s/in_marker//;
I think this needs a backslash in front of the  symbol, 
and a space after in_marker, i.e. it should be: 
{ @$appendline =~ s/in_marker/\sp/;

That a small issue.  But the following is more
important because it strikes at the ease of
using inheritance of grammars (i.e. patterns).
In
http://www.perl.com/pub/a/2002/08/22/exegesis5.html?page=5#different_diffs
we see the code:
rule fileinfo {
out_marker3 $oldfile:=(\S+) $olddate:=[\h* (\N+?) \h*?] \n
in_marker3  $newfile:=(\S+) $newdate:=[\h* (\N+?) \h*?] \n
}

rule out_marker { \+ sp }
rule in_marker  {  - sp }

The sp means a single literal space.
So I think out_marker3 means look for + + +  
rather than +++ which is what is really needed
to match a Unified diff.  Similarly for in_marker3

Or am I missing something?
If these are bugs, then what would be the best way to
fix the code while retaining as much reuse as possible.

 
Hopefully helpfully yours,
Steve
-- 
Steven Tolkin  [EMAIL PROTECTED]  617-563-0516 
Fidelity Investments   82 Devonshire St. V8D Boston MA 02109
There is nothing so practical as a good theory.  Comments are by me, 
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