Pattern HS

A multi-library Haskell mono-repo providing libraries and tools for working with patterns, subjects, and graph structures. The primary library, pattern, offers a generalized representation of graph elements, including nodes, relationships, paths and compositions.

Quick Start

Installation

Prerequisites:

• GHC 9.12.2
• Cabal 3.6.2.0 or later

Using ghcup:

ghcup install ghc 9.12.2
ghcup set ghc 9.12.2
ghcup install cabal
ghcup set cabal

Clone with submodules (required for corpus tests):

# When cloning for the first time
git clone --recurse-submodules <repository-url>

# Or if already cloned, initialize submodules
git submodule update --init --recursive

The corpus tests require the tree-sitter-gram submodule to be initialized at libs/gram/test-data/tree-sitter-gram. Tests will skip gracefully if the submodule is not initialized.

Add to your project:

build-depends:
  - pattern

Basic Usage

import Pattern.Core (pattern, patternWith)

-- Create an atomic pattern
atomA = pattern "A"

-- Create a pattern with elements
atomB = pattern "B"
relationship = patternWith "knows" [atomA, atomB]

JSON and Schema Generation

# Convert Gram notation to canonical JSON
gramref parse pattern.gram --format json --value-only --canonical

# Bidirectional conversion: Gram ↔ JSON
gramref convert pattern.json --from json --to gram

# Generate JSON Schema
gramref schema --format json-schema > pattern-schema.json

# Generate TypeScript types
gramref schema --format typescript > pattern.ts

# Generate Rust types
gramref schema --format rust > pattern.rs

Documentation

• User Documentation - Complete user guide with examples
• Reference Documentation - For language porters
• Canonical JSON Format - JSON format specification with examples
• User Documentation: docs/ - User-facing guides and API documentation
  • Pattern Construction Functions - Guide to point, pattern, and pure with porting guidance
  • Gram Serialization - Serialization, JSON, and schema generation
• Design Documentation: design/DESIGN.md - Category-theoretic framework and design principles
• Implementation Roadmap: TODO.md - Planned features and implementation phases
• Feature Specifications: specs/ - Detailed specifications for each feature
• API Documentation: Generate with cabal haddock or see specs/*/contracts/type-signatures.md
• Quickstart Guide: specs/002-basic-pattern-type/quickstart.md

Testing

Run the full test suite:

cabal test all

Important Test Requirements:

• JSON Roundtrip Tests: All patterns must successfully roundtrip through JSON serialization (gram:test:gram-test --match=Roundtrip)
• Corpus Tests: Require tree-sitter-gram submodule initialized (tests skip gracefully if not present)
• Property-Based Tests: QuickCheck validates 100+ random patterns for structural integrity

Libraries

• pattern: Core pattern data structure library (recursive, decorated sequences)
• subject: Special data structure with index, labels, and property record
• gram: Serialization/deserialization for "Subject Patterns"
  • Gram notation (text) serialization
  • Canonical JSON with bidirectional conversion
  • JSON Schema generation (Draft 2020-12)
  • TypeScript and Rust type generation for downstream ports

Project Structure

pattern-hs/
├── libs/
│   ├── pattern/             # Pattern library
│   ├── subject/             # Subject library
│   └── gram/                # Gram library
├── docs/
│   ├── guide/               # User-facing documentation
│   └── reference/           # Porter-facing documentation
└── apps/
    └── gramref-cli/         # CLI tool for testing and validation

Design Goals

• Typeclass Instances: Show ✅, Eq ✅, Functor ✅, Foldable ✅, Traversable (Phase 2-6)
• Constructor Functions: point (atomic) and pattern (with elements) (Phase 3)
• Classification Functions: isNode, isRelationship, isSubgraph, isPath (Phase 8-11)
• Navigation Functions: source, target, nodes, relationships (Phase 12)
• Graph Views: GraphView typeclass and implementations (Phase 15)
• Query Functions: length, size, depth (Phase 7)

1. Reference Implementation: Canonical reference design for translation to other languages
2. Category-Theoretic Foundation: Built on solid mathematical foundations
3. Schema-Lazy Design: Patterns don't commit to specific graph semantics at creation time
4. Multi-Language Translation: Design prioritizes clarity and mathematical correctness

Contributing

This is a reference implementation with strict quality standards. See .specify/memory/constitution.md for development principles.

Workflow Requirements:

• ALWAYS work in a feature branch - Never commit directly to main
• Use the Speckit workflow (/speckit.specify, /speckit.plan, /speckit.tasks)
• Follow the Constitution principles

License

BSD-3-Clause (see LICENSE file)