diff options
Diffstat (limited to 'txr.1')
| -rw-r--r-- | txr.1 | 46 |
1 files changed, 23 insertions, 23 deletions
@@ -648,37 +648,37 @@ and can also be used as a subexpression term for some operators. The expression a| means (a|): match either a, or nothing. It's not possible to pass the empty regex to some operators; for instance (*) is a syntax error, not the * operator with an empty string on the left. -.IP (RE) -If RE is a regular expression, then so is (RE). +.IP (R) +If R is a regular expression, then so is (R). The contents of parentheses denote one regular expression unit, so that for instance in (RE)*, the * operator applies to the entire parenthesized group. The syntax () is valid and equivalent to the empty regular expression. -.IP (RE)? -optionally match the preceding regular expression (RE). -.IP (RE)+ -match the preceding expression one or more times, as many times as possible. -.IP (RE)* -match the preceding expression zero or more times, as many times - as possible. This operator is sometimes called the "Kleene operator". -.IP (RE1)%(RE2) -match RE1 zero or more times, but not as many times as possible: stop the -match at the first point where RE2 matches, even if repetitions of RE1 can -continue matching. This is called the non-greedy operator. RE2 may be -an empty regular expression, in which case this is equivalent to (RE1)*. -.IP ~(RE) -match the complement of the following expression; i.e. match -those texts that (RE) does not match. This operator is called complement, +.IP R? +optionally match the preceding regular expression R. +.IP R+ +match the preceding expression R one or more times, as many times as possible. +.IP R* +match the expression R zero or more times, as many times as possible. This +operator is sometimes called the "Kleene operator" or "Kleene star". +.IP R1%R2 +match R1 zero or more times, but not as many times as possible: stop the +match at the first point where R2 matches, even if repetitions of R1 can +continue matching. This is called the non-greedy operator. R2 may be +an empty regular expression, in which case this is equivalent to R1*. +.IP ~R +match the complement of the following expression R; i.e. match +those texts that R does not match. This operator is called complement, or logical not. -.IP (RE1)(RE2) +.IP R1R2 Two consecutive regular expressions denote catenation: the left expression must match, and then the right. -.IP (RE1)|(RE2) -match either the expression RE1 or RE2. This operator is called union, +.IP R1|R2 +match either the expression R1 or R2. This operator is called union, logical or, or disjunction. -.IP (RE1)&(RE2) -match both the expression RE1 and RE2 simultaneously; i.e. the +.IP R1&R2 +match both the expression R1 and R2 simultaneously; i.e. the matching text must be one of the texts which are in the intersection of the set -of texts matched by RE1 and the set matched by RE2. This operator is called +of texts matched by R1 and the set matched by R2. This operator is called intersection, logical and, or conjunction. .PP |