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Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 45 |
1 files changed, 45 insertions, 0 deletions
@@ -50137,6 +50137,51 @@ The double backslash in the string literal produces a single backslash in the resulting string object that is processed by .codn regex-parse . +.coNP Function @ regex-optimize +.synb +.mets (regex-optimize << regex-tree-syntax ) +.syne +.desc +The +.code regex-compile +function accepts the source code of a regular expression, +expressed as a Lisp data structure representing an abstract syntax tree, +and calculates an equivalent structure in which certain simplifications +have been performed, or in some cases substitutions which eliminate the +dependence on derivative-based processing. + +The +.meta regex-tree-syntax +is assumed to be correct, as if it were produced by the +.code regex-parse +or +.code regex-from-trie +functions. Incorrect syntax produces unspecified results; an exception may be +thrown, or some object may appear to be successfully returned. + +Note: it is unnecessary to call this function to prepare the input for +.code regex-compile +because that function optimizes internally. However, the source code attached +to a compiled regular expression object is the original unoptimized syntax +tree, and that is used for rendering the +.code #/.../ +notation when the object is printed. If the syntax is passed through +.code regex-optimize +before +.codn regex-compile , +the resulting object will have the optimized code attached to it, and +subsequently render that way in printed form. + +.TP* Examples: + +.verb + ;; a|b|c -> [abc] + (regex-optimize '(or #\ea (or #\eb #\ec))) -> (set #\ea #\eb #\ec) + + ;; (a|) -> a? + (regex-optimize '(or #\ea nil)) -> (? #\ea) +.brev + .coNP Function @ read-until-match .synb .mets (read-until-match < regex >> [ stream <> [ include-match ]]) |