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Say I want to match the a character "h a" or "f a". So capture all the a that are preceded by an h or an f.
I tried the following :
1) \(h\|f\) \\(a\\)
but it doesn't work. the problem appears to be with the the OR group, if I do
2) h \\(a\\) the a in the string h a is captured.
Does anyone know how to fix my first expression?
There's a clear difference between the group that is working:
\\(...\\)
and the group that is not working:
\(...\)
You need to double your backslashes in the non-working group (and for \\| as well).
In elisp backslashes are special to both the double-quoted string syntax and the regexp syntax, so when regexps are represented as double-quoted strings you need to double-escape the backslashes which are intended for the regular expression.
