如何在TCL中匹配整个单词？ regexp“ \\\\ msub1 \\\\ M” sub1_ex

Question

Please help me in solving this...

set var1 sub1
set var2 sub
set var3 sub1_ex

i want to match $var1 and $var3 and not $var2 ie

regexp $var1 $var3 should be 1 ; regexp $var2 $var3 should be 0 ; but getting 1.

I also tried

regexp "\\m$var1\\M" $var3

but got 0.

Answer 1

Okay, I think I finally managed to parse the question.

The first problem is that "sub" is a substring of "sub1", and they're both substrings of "sub1_ex".

The second problem is that "words" in terms of the regular expression engine are contigous blocks of adjacent characters matching class \\w which includes both alphanumerics and an underscore (see this ), so if you use \\m and \\M to anchor the pattern "sub1", the string "sub1_ex" would not match as there's no word boundary between "1" and "_".

What to try next does really depend on your use case and unfortunately I'm not quite getting it. Changing var2 to read sub\\M would probably fix it but I'm not sure it's what you want.

Answer 2

The problem you've got is that the word character class includes the underscore character, so the special “at start/end of word” patterns don't work for you.

A partial solution is to use a more elaborate match:

regexp "\\m${var1}(?!\[a-zA-Z0-9\])" $var3

This works at the end of a word, but not at the start (the RE engine used in Tcl does not support any kind of lookbehind constraint). Thus, it is actually simpler to transform the string being matched against:

regexp "\\m$var1\\M" [string map {"_" " "} $var3]

That will work fine provided the string you're trying to find doesn't include an underscore. I guess that's true in your case. If not, you have to use a real trick and insert some really rare character as the replacement:

set mapping {"_" "\ufffd"};   # Unicode replacement char!
regexp "\\m[string map $mapping $var1]\\M" [string map $mapping $var3]