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| -rw-r--r-- | Doc/lib/libre.tex | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex index 45b1ca5..aa18814 100644 --- a/Doc/lib/libre.tex +++ b/Doc/lib/libre.tex @@ -61,13 +61,14 @@ matches a particular string, which comes down to the same thing). Regular expressions can be concatenated to form new regular expressions; if \emph{A} and \emph{B} are both regular expressions, -then \emph{AB} is also an regular expression. If a string \emph{p} +then \emph{AB} is also a regular expression. If a string \emph{p} matches A and another string \emph{q} matches B, the string \emph{pq} -will match AB. Thus, complex expressions can easily be constructed -from simpler primitive expressions like the ones described here. For -details of the theory and implementation of regular expressions, -consult the Friedl book referenced below, or almost any textbook about -compiler construction. +will match AB if \emph{A} and \emph{B} do no specify boundary +conditions that are no longer satisfied by \emph{pq}. Thus, complex +expressions can easily be constructed from simpler primitive +expressions like the ones described here. For details of the theory +and implementation of regular expressions, consult the Friedl book +referenced below, or almost any textbook about compiler construction. A brief explanation of the format of regular expressions follows. For further information and a gentler presentation, consult the Regular @@ -138,9 +139,11 @@ not five. \var{m} to \var{n} repetitions of the preceding RE, attempting to match as many repetitions as possible. For example, \regexp{a\{3,5\}} will match from 3 to 5 \character{a} characters. Omitting \var{n} -specifies an infinite upper bound; you can't omit \var{m}. The comma -may not be omitted or the modifier would be confused with the -previously described form. +specifies an infinite upper bound; you can't omit \var{m}. As an +example, \regexp{a\{4,\}b} will match \code{aaaab}, a thousand +\character{a} characters followed by a \code{b}, but not \code{aaab}. +The comma may not be omitted or the modifier would be confused with +the previously described form. \item[\code{\{\var{m},\var{n}\}?}] Causes the resulting RE to match from \var{m} to \var{n} repetitions of the preceding RE, |