Implementing peg2pegtl, based on abnf2pegtl.

include/tao/pegtl/contrib/peg.hpp

@@ -0,0 +1,188 @@
+// Copyright (c) 2021 Daniel Deptford
+// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
+
+#ifndef TAO_PEGTL_CONTRIB_PEG_HPP
+#define TAO_PEGTL_CONTRIB_PEG_HPP
+
+#include <tao/pegtl.hpp>
+
+namespace TAO_PEGTL_NAMESPACE::peg
+{
+   // PEG grammar from https://pdos.csail.mit.edu/~baford/packrat/popl04/peg-popl04.pdf
+
+   // clang-format off
+   struct AND;
+   struct Char;
+   struct Class;
+   struct CLOSE;
+   struct Comment;
+   struct Definition;
+   struct DOT;
+   struct EndOfFile;
+   struct EndOfLine;
+   struct Expression;
+   struct QUESTION;
+   struct IdentCont;
+   struct Identifier;
+   struct IdentStart;
+   struct LEFTARROW;
+   struct Literal;
+   struct NOT;
+   struct OPEN;
+   struct PLUS;
+   struct Prefix;
+   struct Primary;
+   struct Range;
+   struct Sequence;
+   struct SLASH;
+   struct Space;
+   struct Spacing;
+   struct STAR;
+   struct Suffix;
+
+   struct Grammar : tao::pegtl::seq<Spacing, tao::pegtl::plus<Definition>, EndOfFile> {};
+   struct Definition : tao::pegtl::seq<Identifier, LEFTARROW, Expression> {};
+   struct Expression : tao::pegtl::seq<
+     Sequence,
+     tao::pegtl::star<
+       tao::pegtl::seq<
+         SLASH,
+         Sequence
+       >
+     >
+   > {};
+   struct Sequence : tao::pegtl::star<Prefix> {};
+   struct Prefix : tao::pegtl::seq<
+     tao::pegtl::opt<
+       tao::pegtl::sor<
+         AND,
+         NOT
+       >
+     >,
+     Suffix
+   > {};
+
+   struct Suffix : tao::pegtl::seq<
+     Primary,
+     tao::pegtl::opt<
+       tao::pegtl::sor<
+         QUESTION,
+         STAR,
+         PLUS
+       >
+     >
+   > {};
+
+   struct Primary : tao::pegtl::sor<
+     tao::pegtl::seq<Identifier, tao::pegtl::not_at<LEFTARROW> >,
+     tao::pegtl::seq<OPEN, Expression, CLOSE>,
+     Literal,
+     Class,
+     DOT> {};
+
+   struct Identifier : tao::pegtl::seq<IdentStart, tao::pegtl::star<IdentCont>, Spacing> {};
+
+   struct IdentStart : tao::pegtl::ranges< 'a', 'z', 'A', 'Z', '_' > {};
+
+   struct IdentCont : tao::pegtl::sor<
+     IdentStart,
+     tao::pegtl::range<'0','9'>
+   > {};
+
+   struct Literal : tao::pegtl::sor<
+     tao::pegtl::seq<
+       tao::pegtl::one<'\''>,
+       tao::pegtl::star<
+          tao::pegtl::seq<
+            tao::pegtl::not_at<
+              tao::pegtl::one<'\''>
+            >,
+            Char
+          >
+       >,
+       tao::pegtl::one<'\''>,
+       Spacing
+     >,
+     tao::pegtl::seq<
+       tao::pegtl::one<'\"'>,
+       tao::pegtl::star<
+         tao::pegtl::seq<
+            tao::pegtl::not_at<tao::pegtl::one<'\"'> >,
+            Char
+          >
+       >,
+       tao::pegtl::one<'\"'>,
+       Spacing
+     >
+   > {};
+
+   struct Class : tao::pegtl::seq<
+     tao::pegtl::one<'['>,
+     tao::pegtl::star<
+       tao::pegtl::seq<
+         tao::pegtl::not_at<tao::pegtl::one<']'> >,
+         Range
+       >
+     >,
+     tao::pegtl::one<']'>,
+     Spacing
+   > {};
+
+   struct Range : tao::pegtl::sor<
+     tao::pegtl::seq<
+       Char,
+       tao::pegtl::one<'-'>,
+       Char>,
+     Char
+   > {};
+
+   struct Char : tao::pegtl::sor<
+     tao::pegtl::seq<
+       tao::pegtl::one<'\\'>,
+       tao::pegtl::one<'n','r','t','\'','\"','[',']','\\'> >,
+     tao::pegtl::seq<
+       tao::pegtl::one<'\\'>,
+       tao::pegtl::range<'0','2'>,
+       tao::pegtl::range<'0','7'>,
+       tao::pegtl::range<'0','7'> >,
+     tao::pegtl::seq<
+       tao::pegtl::one<'\\'>,
+       tao::pegtl::range<'0','7'>,
+       tao::pegtl::opt<tao::pegtl::range<'0','7'> > >,
+     tao::pegtl::seq<
+       tao::pegtl::not_at<tao::pegtl::one<'\\'> >,
+       tao::pegtl::any>
+     > {};
+
+   struct LEFTARROW : tao::pegtl::seq<tao::pegtl::string<'<','-'>, Spacing> {};
+   struct SLASH : tao::pegtl::seq<tao::pegtl::one<'/'>, Spacing> {};
+   struct AND : tao::pegtl::seq<tao::pegtl::one<'&'>, Spacing> {};
+   struct NOT : tao::pegtl::seq<tao::pegtl::one<'!'>, Spacing> {};
+   struct QUESTION : tao::pegtl::seq<tao::pegtl::one<'?'>, Spacing> {};
+   struct STAR : tao::pegtl::seq<tao::pegtl::one<'*'>, Spacing> {};
+   struct PLUS : tao::pegtl::seq<tao::pegtl::one<'+'>, Spacing> {};
+   struct OPEN : tao::pegtl::seq<tao::pegtl::one<'('>, Spacing> {};
+   struct CLOSE : tao::pegtl::seq<tao::pegtl::one<')'>, Spacing> {};
+   struct DOT : tao::pegtl::seq<tao::pegtl::one<'.'>, Spacing> {};
+
+   struct Spacing : tao::pegtl::star<tao::pegtl::sor<Space, Comment> > {};
+   struct Comment :
+   tao::pegtl::seq<
+     tao::pegtl::one<'#'>,
+     tao::pegtl::star<
+       tao::pegtl::seq<
+         tao::pegtl::not_at<EndOfLine>,
+         tao::pegtl::any
+       >
+     >,
+     EndOfLine
+   > {};
+
+   struct Space : tao::pegtl::sor<tao::pegtl::one<' '>, tao::pegtl::one<'\t'>, EndOfLine> {};
+   struct EndOfLine : tao::pegtl::sor<tao::pegtl::string<'\r','\n'>, tao::pegtl::one<'\n'>, tao::pegtl::one<'\r'> > {};
+   struct EndOfFile : tao::pegtl::eof {};
+   // clang-format on
+
+}  // namespace TAO_PEGTL_NAMESPACE::peg
+
+#endif

src/example/pegtl/CMakeLists.txt

@@ -26,6 +26,7 @@ set(example_sources
   modulus_match.cpp
   parse_tree.cpp
   parse_tree_user_state.cpp
+  peg2pegtl.cpp
   proto3.cpp
   random_order.cpp
   recover.cpp

src/example/pegtl/peg.peg

@@ -0,0 +1,37 @@
+# Parsing Expression Grammar (PEG) taken from
+# https://pdos.csail.mit.edu/~baford/packrat/popl04/peg-popl04.pdf
+
+# Hierarchical syntax
+Grammar <- Spacing Definition+ EndOfFile
+Definition <- Identifier LEFTARROW Expression
+Expression <- Sequence (SLASH Sequence)*
+Sequence <- Prefix*
+Prefix <- (AND / NOT)? Suffix
+Suffix <- Primary (QUESTION / STAR / PLUS)?
+Primary <- Identifier !LEFTARROW / OPEN Expression CLOSE / Literal / Class / DOT
+
+# Lexical syntax
+Identifier <- IdentStart IdentCont* Spacing
+IdentStart <- [a-zA-Z_]
+IdentCont <- IdentStart / [0-9]
+Literal <- ['] (!['] Char)* ['] Spacing / ["] (!["] Char)* ["] Spacing
+Class <- '[' (!']' Range)* ']' Spacing
+Range <- Char '-' Char / Char
+Char <- '\\' [nrt'"\[\]\\] / '\\' [0-2][0-7][0-7] / '\\' [0-7][0-7]? / !'\\' .
+
+LEFTARROW <- '<-' Spacing
+SLASH <- '/' Spacing
+AND <- '&' Spacing
+NOT <- '!' Spacing
+QUESTION <- '?' Spacing
+STAR <- '*' Spacing
+PLUS <- '+' Spacing
+OPEN <- '(' Spacing
+CLOSE <- ')' Spacing
+DOT <- '.' Spacing
+
+Spacing <- (Space / Comment)*
+Comment <- '#' (!EndOfLine .)* EndOfLine
+Space <- ' ' / '\t' / EndOfLine
+EndOfLine <- '\r\n' / '\n' / '\r'
+EndOfFile <- !.