Division of Nearshore Research | ScottDuff / Perl6Apocalypse5

Notes on Apocalypse 5 [1]

Brave new world

	(...) capturing brackets
	[...] grouping brackets (non capturing)
	{...} closure (return value ignored unless assigned)
	<...> Assertion (does this thing match?)
	:...  introduces a meta-syntactic token (a modifier)

$0 is the match object. Assigning to $0 affects the return value of the RE

qr is replaced rx and isn't a quote-like operator
equivalent of perl5's /x modifier is always on in perl6 rules
^ and $ now always match the start and end of the string
$ no longer matches before optional newline at the end of a string
^^ and $$ match the start and end of lines within a string
\n matches any form of "newline", not just current-system-specific
: (colon) controls backtracking (see also <commit> below)
- : means don't backtrack to previous atom
- :: means don't backtrack and the entire group fails
- ::: means don't backtrack and the entire rule fails

Built-in regular expression modifiers

Modifiers now come at the beginning of the RE statement and as such, the leading m or s is required. For example, s:i/foo/bar/ replaces "foo", "Foo", "FOO", etc with bar. The modifer :i means "ignore case".

Long Modifier	Short Modifier	Meaning
:cont	:c	Continue from where the previous match left off
:words	:w	Match a sequence of "words". Causes whitespace (which is normally ignored) to be replaced by \s+ between identifier and \s* anywhere else
:ignorecase	:i	Match all alphabetic characters in a case insensitive manner
:any	:a	returns a list of anywhere the pattern matches within the string regardless of overlap
:each	:e	apply the pattern iteratively ("each" time we can)
:once	:o	Match succeeds exactly once. To allow the RE to match again, execute the .reset() method on the RE object.
:perl5	:p5	Perl 5 matching. Cause the RE to be interpreted using the Perl 5 rules
?	:u0	Level 0 Unicode support. A . (dot) matches bytes
?	:u1	Level 1 Unicode support. A . (dot) matches code points
?	:u2	Level 2 Unicode support. A . (dot) matches a grapheme
?	:u3	Level 3 Unicode support. What . (dot) matches is language dependent
:nth(1)	:1st	only match the first occurance of the pattern
:nth(2)	:2nd	only match the second occurance of the pattern
:nth(3)	:3rd	only match the third occurance of the pattern
:nth(4)	:4th	only match the fourth occurance of the pattern
:nth(5)	:5th	only match the fifth occurance of the pattern
...	...	...
:x(1)	:1x	Match one time
:x(2)	:2x	Match two times
:x(3)	:3x	Match three times
...	...	...

Built-in assertions

assertion	meaning
<[...]>	matches ... as a character class
<'...'>	matches ... as a literal string
<alpha>	matches any alphabetic character
<digit>	matches any numeric character
<sp>	matches a space character
<ws>	matches any sequences of whitespace (same as \s+)
<dot>	matches a literal . character (same as <'.'>)
<lt>	matches a litereal < character (same as <'<'>)
<gt>	matches a litereal > character (same as <'>'>)
<prior>	match whatever the most recently successful match did
<after pattern>	matches only after pattern (zero-width)
<before pattern>	matches only before pattern (zero-width)
<commit>	fails the entire match if backtracked to
<cut>	fails the entire match if backtracked to and removes the portion of the string that matched to that point
<fail>	causes the match to fail if reached
<null>	match nothing
<ident>	match an "identifier". (same as [ [<alpha>\|_] \w* ])
<self>	matches the same pattern as the current rule (useful for recursion)

From Division of Nearshore Research

ScottDuff: Perl6Apocalypse5

Built-in regular expression modifiers

Built-in assertions