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rregexpcre

split character at deliminator conditionally negative lookahead assertion

I want to split a string at . or : unless the next character is )

Following this question: R strsplit: Split based on character except when a specific character follows why isn't 

strsplit("Glenelg (Vic.)",'\\.|:(?!\\))', perl = TRUE)

returning 

[[1]]
[1] "Glenelg (Vic)"

instead it splits at the ., like so: 

[1] "Glenelg (Vic" ")"
Solution

  • It is not grouped correctly. \.|:(?!\)) matches a . anywhere in a string or a : not followed with ). If you group . and : patterns, '(?:\\.|:)(?!\\))', it will work.

    However, you may use a better regex version based on a character class:

    strsplit("Glenelg (Vic.)",'[.:](?!\\))', perl = TRUE)
[[1]]
[1] "Glenelg (Vic.)"

    Here, [.:](?!\)) matches either . or : that are both not immediately followed with ).

    See the regex demo.