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Diffstat (limited to 'doc/regexprs.txt')
| -rw-r--r--[-rwxr-xr-x] | doc/regexprs.txt | 42 |
1 files changed, 22 insertions, 20 deletions
diff --git a/doc/regexprs.txt b/doc/regexprs.txt index 930352948..fa7f9d24a 100755..100644 --- a/doc/regexprs.txt +++ b/doc/regexprs.txt @@ -44,19 +44,21 @@ As the regular expressions supported by this module are enormous, the reader is referred to http://perldoc.perl.org/perlre.html for the full documentation of Perl's regular expressions. -Because the backslash ``\`` is a meta character both in the Nimrod +Because the backslash ``\`` is a meta character both in the Nim programming language and in regular expressions, it is strongly -recommended that one uses the *raw* strings of Nimrod, so that -backslashes are interpreted by the regular expression engine:: +recommended that one uses the *raw* strings of Nim, so that +backslashes are interpreted by the regular expression engine: +```nim r"\S" # matches any character that is not whitespace +``` A regular expression is a pattern that is matched against a subject string from left to right. Most characters stand for themselves in a pattern, and match the corresponding characters in the subject. As a trivial example, -the pattern:: +the pattern: - The quick brown fox + The quick brown fox matches a portion of a subject string that is identical to itself. The power of regular expressions comes from the ability to include @@ -80,13 +82,13 @@ meta character meaning ``|`` start of alternative branch ``(`` start subpattern ``)`` end subpattern -``?`` extends the meaning of ``(`` - also 0 or 1 quantifier - also quantifier minimizer -``*`` 0 or more quantifier -``+`` 1 or more quantifier - also "possessive quantifier" ``{`` start min/max quantifier +``?`` extends the meaning of ``(`` + | also 0 or 1 quantifier (equal to ``{0,1}``) + | also quantifier minimizer +``*`` 0 or more quantifier (equal to ``{0,}``) +``+`` 1 or more quantifier (equal to ``{1,}``) + | also "possessive quantifier" ============== ============================================================ @@ -128,7 +130,7 @@ in patterns in a visible manner. There is no restriction on the appearance of non-printing characters, apart from the binary zero that terminates a pattern, but when a pattern is being prepared by text editing, it is usually easier to use one of the following escape sequences than the binary character it -represents:: +represents: ============== ============================================================ character meaning @@ -146,7 +148,7 @@ character meaning After ``\x``, from zero to two hexadecimal digits are read (letters can be in upper or lower case). In UTF-8 mode, any number of hexadecimal digits may appear between ``\x{`` and ``}``, but the value of the character code must be -less than 2**31 (that is, the maximum hexadecimal value is 7FFFFFFF). If +less than 2^31 (that is, the maximum hexadecimal value is 7FFFFFFF). If characters other than hexadecimal digits appear between ``\x{`` and ``}``, or if there is no terminating ``}``, this form of escape is not recognized. Instead, the initial ``\x`` will be interpreted as a basic hexadecimal escape, @@ -175,17 +177,17 @@ for themselves. For example: example meaning ============== ============================================================ ``\040`` is another way of writing a space -``\40`` is the same, provided there are fewer than 40 previous +``\40`` is the same, provided there are fewer than 40 previous capturing subpatterns ``\7`` is always a back reference ``\11`` might be a back reference, or another way of writing a tab ``\011`` is always a tab ``\0113`` is a tab followed by the character "3" -``\113`` might be a back reference, otherwise the character with +``\113`` might be a back reference, otherwise the character with octal code 113 -``\377`` might be a back reference, otherwise the byte consisting +``\377`` might be a back reference, otherwise the byte consisting entirely of 1 bits -``\81`` is either a back reference, or a binary zero followed by +``\81`` is either a back reference, or a binary zero followed by the two characters "8" and "1" ============== ============================================================ @@ -224,7 +226,7 @@ current matching point is at the end of the subject string, all of them fail, since there is no character to match. For compatibility with Perl, ``\s`` does not match the VT character (code 11). -This makes it different from the the POSIX "space" class. The ``\s`` characters +This makes it different from the POSIX "space" class. The ``\s`` characters are HT (9), LF (10), FF (12), CR (13), and space (32). A "word" character is an underscore or any character less than 256 that is @@ -240,11 +242,11 @@ even when Unicode character property support is available. Simple assertions ----------------- -The fourth use of backslash is for certain `simple assertions`:idx:. An +The fourth use of backslash is for certain `simple assertions`:idx:. An assertion specifies a condition that has to be met at a particular point in a match, without consuming any characters from the subject string. The use of subpatterns for more complicated assertions is described below. The -backslashed assertions are:: +backslashed assertions are: ============== ============================================================ assertion meaning |