How to ignore special characters

[balajee]

Hi,
Is there a way to ignore special characters while doing regexp. For
Eg, I am getting the following error while doing regexp in one of my
scripts.

% regexp $a $b
couldn't compile regular expression pattern: parentheses () not
balanced

This is expected because I have unbalanced braces in my variables.
But, I can not modify the variables due to other reasons. I want to
ignore all special characters like ),(,- etc. Please let me know if
anybody has any idea.

Thanks,
Balajee

[Uwe Klein]

run your $a through a proc that escapes all specials?

proc re_escape expr {
set expr [ split $expr {} ]
foreach char $expr {
switch -- $char \
( - ) {
lappend res \\ $char
} \{ - \} {
lappend res \\ $char
} \[ - \] {
lappend res \\ $char
} .... - ... {
# more?
} default {
lappend res $char
}
}
return [join $res {}]
}

uwe

[arjenmarkus]

Hello,

characters are escaped via \. For instance:

regexp {\(.*} $someString

to find the (longest) substring starting with a open parenthesis.

To escape all (, ), ...:

regexp [string map {( \\( ) ) \\) ...} $a] $b

The [string map] command is powerful but be aware: it substitutes all
patterns without regard for context.

Regards,

Arjen

[Bruce]

If you want to ignore *all* special characters, the you could just
switch to using [string first ...]

if you really want to use regexp, but want to match literal strings
you could follow the opthers advice to pre-process and escape all
special characters or use one of the following:

regexp "***=$a" $b

or

regexp "(?q)$a" $b


If you wnt to allow *some* special characters but not others, then
you will need to do the escaping yourself.

Bruce

[Wouter Snels]

Op 07-10-11 10:57, balajee schreef:

% set list
a bc \{ \ ] )
% split $list
a bc {\{} \\ \] )
% set list
a bc \{ \ ] )
% string map {\{ \\{ \} \\} \\ \\\\ \[ \\[ \] \\] \( \\( \) \\) \" \\"
\' \\'} $list
a bc \\\{ \\ \] \)
%

Regards, ..