Hi! I am learning regular expressions in recent times. When I use writeLines() function, I got a unexpected result. I think writeLines("12\bd") will output 12d, but it output 1d in reality. The digit in front of \b seems to be hidden. Could you help me explain this result?
I don't think writeLines() uses regular expressions at all. Regular expressions are used to match text and writeLines() is simple writing text. I don't know what writeLines() is doing with the \b combination, but understanding it will not help you use regular expressions.
You might find working with a function like sub() more useful.
sub(pattern = "12\\b", "X", "there are 12 fish")
[1] "there are X fish"
> sub(pattern = "12\\b", "X", "there are 123 fish")
[1] "there are 123 fish"
Notice I use a double back slash. I think that is necessary because both R and the regular expression engine interpret the \ character.
OK, thanks. I just konw \b actually rewind the cursor one bit.
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