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| -rw-r--r-- | bp.1.md | 14 |
1 files changed, 12 insertions, 2 deletions
@@ -202,10 +202,20 @@ zero or more comma-separated words) instances of *skip* (e.g. **\`\"..\`\" % (\`\\.)**) **\<** *pat* -: Just after *pat* (lookbehind) +: Matches at the current position if *pat* matches immediately before the +current position (lookbehind). Conceptually, you can think of this as creating +a file containing only the *N* characters immediately before the current +position and attempting to match *pat* on that file, for all values of *N* from +the minimum number of characters *pat* can match up to maximum number of +characters *pat* can match (or the length of the current line upto the current +position, whichever is smaller). **Note:** For fixed-length lookbehinds, this +is quite efficient (e.g. **\<(100\`x)**), however this could cause performance +problems with variable-length lookbehinds (e.g. **\<(\`x 0-100\`y)**). Also, +it is not advised to use **\^**, **\^\^**, **$**, or **$$** inside a lookbehind, +as they will match against the edges of the lookbehind slice. **\>** *pat* -: Just before *pat* (lookahead) +: Matches *pat*, but does not consume any input (lookahead). **\@** *pat* : Capture *pat* |