diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/next.n | 8 | ||||
| -rw-r--r-- | doc/re_syntax.n | 26 |
2 files changed, 30 insertions, 4 deletions
@@ -96,9 +96,11 @@ forward to the proper implementation of the method (which it does by invoking the \fBnext\fR command as filters are inserted into the front of the method call chain) and is responsible for returning the result of \fBnext\fR. .PP -Filters are not invoked when processing an invocation of the \fBunknown\fR -method because of a failure to locate a method implementation, or when -invoking either constructors or destructors. +Filters are invoked when processing an invokation of the \fBunknown\fR +method because of a failure to locate a method implementation, but \fInot\fR +when invoking either constructors or destructors. (Note however that the +\fBdestroy\fR method is a conventional method, and filters are invoked as +normal when it is called.) .SH EXAMPLES .PP This example demonstrates how to use the \fBnext\fR command to call the diff --git a/doc/re_syntax.n b/doc/re_syntax.n index 46a180d..7988071 100644 --- a/doc/re_syntax.n +++ b/doc/re_syntax.n @@ -683,9 +683,33 @@ earlier in the RE taking priority over ones starting later. Note that outer subexpressions thus take priority over their component subexpressions. .PP -Note that the quantifiers \fB{1,1}\fR and \fB{1,1}?\fR can be used to +The quantifiers \fB{1,1}\fR and \fB{1,1}?\fR can be used to force longest and shortest preference, respectively, on a subexpression or a whole RE. +.RS +.PP +\fBNOTE:\fR This means that you can usually make a RE be non-greedy overall by +putting \fB{1,1}?\fR after one of the first non-constraint atoms or +parenthesized sub-expressions in it. \fIIt pays to experiment\fR with the +placing of this non-greediness override on a suitable range of input texts +when you are writing a RE if you are using this level of complexity. +.PP +For example, this regular expression is non-greedy, and will match the +shortest substring possible given that +.QW \fBabc\fR +will be matched as early as possible (the quantifier does not change that): +.PP +.CS +ab{1,1}?c.*x.*cba +.CE +.PP +The atom +.QW \fBa\fR +has no greediness preference, we explicitly give one for +.QW \fBb\fR , +and the remaining quantifiers are overridden to be non-greedy by the preceding +non-greedy quantifier. +.RE .PP Match lengths are measured in characters, not collating elements. An empty string is considered longer than no match at all. For example, |