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PEGEX: A PEG-based pattern matching library EXtended by back reference with regex-like notation in Scala

PEGEX (Parsing Expression Grammar EXtended by back reference with regex-like notations) is a PEG-like pattern matching library for Scala.
PEGEX provides both power of PEG and light-weight syntax of regular expressions. It accepts a PEG-variant with regex-like notations.
Currently, PEGEXes seem stronger than CFGs and alike Boolean Grammars.

For sbt user

Include the following in your build.sbt to add pegex to your project libraryDependencies:

libraryDependency += "com.github.kmizu" %% "pegex" % "0.3"

Runtime Requirement

• Scala 2.11.X or Scala 2.12.X
• JDK 1.8.0 or later

Build Requirement

• Sbt 0.13.X

Example

See tests.

Syntax of PEGEX

(name=e;)*, where name is name of this rule and e is an expression

Kind of Expressions (e)

Note that in PEGEX, space characters have meanings. Thus, A=; is different from A= ;

• e1e2: sequence of expressions
  • "ab"
  • "ac"
• e1|e2: unordered choice of expressions
  • "a|b"
  • "(ab|bc)"
• e*: zero or more repetition
  • "a*"
• e+: one or more repetition.
  • "a+"
• e?: zero-or-one repetition.
  • "(a|b)?"
• (?=e): positive lookahead.
  • "(?=a)"
• (?!e): negative lookahead
  • "(?!a)"
• (?<name>e): named capture
• \g'E': (recursive) rule invocation of E
  • is identical to #{E}
• \k<name>: back reference of the named capture of name

#{E}$; E=<(?<tag>#{I})>#{E}*</\k<tag>>; I=[a-z]+;

• .: any character.
  • "(?!a)." matches one character except a
• _: success certainly.
• x: one character.
• [f-t...xyz...]: character class. e.g. [a-zA-Z_]