Parsing Expression Grammar

This is a code-centric library for parsing of PEG grammars in .NET, producing strongly typed outputs. It operates via cursors, and ships with cursors for processing text-streams, token-arrays and XML trees. It contains LINQ extensions to cleanly express grammars directly in code using the C# Integrated Query syntax, and an XML based AST for grammars that it can convert to executable code, as well as a grammar for parsing a human-readable syntax into this AST.

Todo: something about performance and expressability.

Todo: overview and concepts

Cursors, Rules and Results.

Grammar helpers are static classes with type definitions and function helpers for creating rules for a specific cursor type, simplifying definitions by omitting the cursor type.

Grammar formats.

Todo: Cursors

TextTokenCursor, TokenCursor and Tokenizer

XNodeCursor

Todo: list of rule types

Terminal rules

Nonterminal rules

Todo: Grammar helpers

• WithFeedback

  Provides an error-boundary around a rule, replacing all inner errors with a single provided error message.

• EndOfInput

  Creates a rule matching the end-of-input token.

• Choice

  Creates a rule that tries match each of its inner rules in turn, returning success when the first rule matches, or error if none match.

• Optional

  Wraps an inner rule, returning its result if successful, or a successful default-result if not.

• ZeroOrOne

  Wraps the Range rule, with min=0 and max=1.

• ZeroOrMore

  Wraps the Range rule, with min=0 and max=infinity

• OneOrMore

  Wraps the Range rule, with min=1 and max=infinity

• Range

• Between

• PositiveLookahead

• NegativeLookahead

• Label

• Chain

• LeftAssociativeRange

TokenGrammar

• Token

  Creates a rule for matching a token. Has overloads for matching a TokenType or aa constant that is specified directly.

XNodeGrammar

• Element

• Structure

• Content

• Attribute

Todo: describe the XML grammar AST

Todo: describe the simple grammar format

Build

Before commiting run

dotnet format

this will use .editorconfig and format all files in the solution.

CI Pipeline

dotnet restore
dotnet format --verify-no-changes
dotnet build -c Release --no-restore
dotnet test -c Release --no-restore --no-build
dotnet pack -c Release --no-restore --no-build