[Tcl-bugs] [ tcl-Bugs-3063568 ] regsub example doesn't perform as advertized

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Bugs item #3063568, was opened at 2010-09-10 12:57
Message generated for change (Comment added) made by dkf
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Category: 43. Regexp
Group: current: 8.6b1
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Jasper  (jaspertheperson)
>Assigned to: Donal K. Fellows (dkf)
Summary: regsub example doesn't perform as advertized

Initial Comment:
It's this one:
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Convert all non-ASCII and Tcl-significant characters into \u escape sequences by using regsub and subst in combination:

# This RE is just a character class for everything "bad"
set RE {[][{};#\\\$\s\u0080-\uffff]}

# We will substitute with a fragment of Tcl script in brackets
set substitution {[format \\\\u%04x [scan "\\&" %c]]}

# Now we apply the substitution to get a subst-string that
# will perform the computational parts of the conversion.
set quoted [subst [regsub -all $RE $string $substitution]]

===========================================
The RE for "bad" characters includes \s which matches all whitespace characters including newline. However, inserting \ before newline before calling subst on a string containing it does not preserve the newline, it causes it to be replaced by a space, so the whole procedure replaces newlines with \u0020

Not sure how to get this to work properly! Little help?

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>Comment By: Donal K. Fellows (dkf)
Date: 2010-09-10 13:43

Message:
Good catch. Newlines need to be handled specially. :-(

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