Open-source alternatives to Expr

RulesEngine is a business logic evaluator for .NET that executes complex rule workflows and dynamic expressions against input data. It functions as a dynamic expression evaluator and an externalized logic framework, allowing the definition and management of business rules in JSON format to change application behavior without recompiling code. The project decouples decision logic from source code by loading policies from external files or databases. It supports the registration of custom classes and methods to extend standard expression capabilities through type injection. The framework cover

govaluate is a Go expression evaluator and runtime logic parser. It functions as a dynamic rule engine that converts string-based expressions into executable operations, allowing for the calculation of mathematical and logical expressions at runtime. The library enables the execution of business rules and custom formulas without recompiling source code. It supports extending evaluation behavior through the injection of external parameters and the execution of user-defined custom functions. The system provides capabilities for dynamic data validation, including regular expression matching and

The Common Expression Language specification is a formal standard for a non-Turing-complete expression language designed for safe, portable, and fast logic evaluation. It serves as a cross-language logic standard and a declarative policy language, providing a consistent semantic framework for executing boolean expressions and data transformations across different programming environments. This specification acts as an embedded expression engine that allows applications to integrate portable logic for evaluating user-defined configurations. It is specifically designed to enable safe user-defin

This project is a Lisp interpreter implementation guide and framework designed to teach the core principles of programming language design. It provides a structured, step-by-step technical framework for building a functional Lisp language from scratch, featuring a specialized interpreter engine and an S-expression parser that converts syntax into abstract syntax trees. The project emphasizes a code-as-data metaprogramming framework, enabling the implementation of macros, quoting, and quasiquoting to transform expressions during evaluation. It is designed with host language agnosticism, allowi

HCL is a configuration language implementation designed for parsing, evaluating, and encoding structured settings through the use of blocks and attributes. It functions as a configuration AST parser and a schema-based decoder that maps attributes and blocks to internal data structures using predefined rules. The project includes an expression evaluation engine that resolves dynamic values and cross-references through multi-phase processing of variables and functions. It also provides a configuration file formatter to standardize the layout and indentation of source code for consistent visual

Power-Fx is a declarative logic framework and low-code formula language based on Excel formulas. It functions as an expression parser and evaluator that transforms formula strings into an abstract syntax tree to execute logical operations and resolve values. The project provides a standardized integration layer to connect formula-based logic to external data sources for querying and pushing records. This allows for the definition of business rules and calculations that can be shared as consistent logic across different applications and platforms.

Oils is a Unix shell interpreter and scripting language runtime that combines a modern shell language with POSIX and Bash compatibility. It functions as a structured data shell, integrating JSON and J8 formats to manage complex data without relying on string parsing. The system is distinguished by a C++ transpiled interpreter that converts a subset of Python source code into strongly typed C++ for high-performance execution. It features a garbage-collected typed runtime that supports prototype-based polymorphism, lexical closures, and reference-based variable mutation. To decouple shell logic

Scriban is a .NET text templating engine and embedded scripting language used for dynamic text generation. It functions as an abstract syntax tree manipulation tool and a template parser, allowing for the conversion of scripts into visitable trees for analysis, modification, and rendering. The engine is specifically designed for Native AOT compatibility, utilizing a reflection-free API to execute templates in trimmed environments. It also provides a dedicated parser and conversion system for Liquid templates, enabling the migration and execution of Liquid scripts within .NET. The project cov

Liquid is a secure template engine and markup language used to generate dynamic HTML or text by combining static templates with backend data. It functions as a web template renderer that transforms markup into final output while restricting available logic to prevent arbitrary code execution. The engine focuses on secure markup execution, providing a restricted environment where user-provided templates cannot access sensitive system data. It utilizes a safe evaluation sandbox to ensure that only a predefined set of instructions can be executed. The system includes capabilities for template s

Boa is a high-performance JavaScript engine and parser designed to execute JavaScript code and analyze source code structure. It functions as a runtime environment for executing scripts to automate tasks or process data, providing both a command-line JavaScript interpreter and a tool for converting source code into abstract syntax trees. The engine is capable of compiling to WebAssembly, allowing the runtime to be deployed and executed within web browser environments. It includes an interactive read-eval-print loop for real-time logic testing and snippet execution via a terminal. The system

Rhai is an embedded scripting engine and dynamically typed language designed for integration into Rust applications. It functions as an abstract syntax tree compiler and native interop layer, allowing developers to map Rust types and functions into a scripting environment for bidirectional communication. The project serves as a framework for creating customizable domain-specific languages. It allows for the definition of custom operators, syntax, and restricted execution environments, enabling the creation of specialized languages with tailored functional sets. The engine covers a broad rang

hogan.js is a logic-less template compiler and Mustache templating engine. It transforms static templates into executable JavaScript functions to generate data-driven strings without using conditional or looping logic. The system focuses on precompilation to eliminate parsing overhead during runtime execution. This includes a precompiled template library and a command line interface for converting template files into optimized JavaScript. The engine handles dynamic content generation through template compilation and data rendering. It supports reusable UI fragments via partials and allows fo

This project is a PHP compatibility library that provides a polyfill for the native ctype extension. It serves as a portability layer, implementing missing core language functions to ensure consistent behavior across different server environments and PHP versions. The library specializes in character type validation, recreating the behavior of native extension functions using pure PHP code. It uses runtime environment detection to identify if the native extension is missing and injects fallback implementations directly into the global namespace to prevent collisions and maintain code portabil

language-ext is a functional programming framework for C# that provides a suite of immutable data structures and monadic types. It enables the implementation of pure functional programming patterns, utilizing containers to manage side effects, optional values, and error handling. The library is distinguished by its advanced concurrency and state management tools, including a software transactional memory system and lock-free atomic references. It also provides specialized utilities for distributed systems, such as vector clocks for causality tracking and deterministic data conflict resolution

Pholcus is a distributed web crawling system designed for large-scale data scraping. It employs a master-worker distribution model to coordinate high-concurrency scraping tasks across a network of remote client nodes, enabling both horizontal and vertical data collection. The system features a hot-loadable rule engine that allows extraction and navigation logic to be updated at runtime without restarting the process. It handles dynamic content through headless browser integration and bypasses bot detection using proxy rotation, automated user authentication, and simulated human behavior. The

Luau is a high-performance programming language evolved from Lua 5.1. It consists of a bytecode virtual machine, an embeddable scripting engine, and a static code analyzer designed to provide a secure, sandboxed execution environment for host applications. The project is distinguished by its gradual typing system, which combines automatic type inference with optional manual annotations to detect bugs without requiring full static typing. It also features native vector mathematics for high-performance operations and a specialized debugging system that uses bytecode patching to minimize executi

TIC-80 is a fantasy console platform and multi-language game engine that provides a virtual retro game development environment. It operates via a bytecode virtual machine that executes game logic within fixed memory and resolution constraints. The project distinguishes itself by offering integrated asset editors for pixel art, tile maps, and a pattern-based chiptune audio workstation all within a single environment. It supports multi-language scripting, allowing developers to write logic in Lua, JavaScript, or Ruby, and provides a standalone game exporter to package projects into native execu

QLExpress is a dynamic scripting engine and expression language for the Java platform. It functions as a runtime expression evaluator and business rule engine, allowing applications to execute scripts and evaluate business logic without requiring system recompilation. The engine distinguishes itself through a secure scripting sandbox that enforces security policies via class whitelisting and execution timeouts. It supports high-precision mathematics to prevent rounding errors and provides language alias support to create domain-specific languages that resemble natural language. Additional cap

Temporal is a distributed workflow orchestration engine designed to manage fault-tolerant, stateful, and long-running background processes. It functions as a platform for coordinating complex cross-service operations, ensuring consistency and reliability in distributed environments by decoupling workflow orchestration from task execution. The platform distinguishes itself through a deterministic, event-sourced execution model that reconstructs workflow state by re-executing code from an immutable event log. This approach isolates non-deterministic side effects into managed activities, allowin

This project is a comprehensive collection of frontend development best practices and standards. It provides guides for writing semantic HTML, efficient CSS, and functional JavaScript to improve overall web performance and accessibility. The repository establishes frameworks for modern CSS architecture, focusing on specificity management and the use of Flexbox and Grid for predictable layouts. It outlines patterns for functional JavaScript programming, emphasizing the use of pure functions and composition to reduce execution time and dependency bloat. The guidelines cover several core capabi

This project provides a server-side language runtime and a standardized Docker image for deploying applications across different operating systems. It functions as an execution environment for generating dynamic HTML, JSON, and XML content, while also serving as a command line interface for automation scripts and background jobs. The runtime is designed for extensibility through a C-based extension architecture, allowing the loading of custom modules for specialized functionality. It supports multiple server application interfaces, including a FastCGI web interface for high-performance commun

AlgoXY is a functional programming educational book and technical publication produced as a LaTeX digital book. It serves as a programming education resource and library focused on functional algorithms and data structures. The project provides a collection of persistent data structures, such as trees and heaps, designed for immutable state management. It includes a series of implementation exercises and verified answers to teach core computer science concepts through the practical application of functional logic. The content covers the design of persistent data structures and the implementa

This project provides a set of software architecture guidelines, Lisp coding standards, and functional programming patterns for Clojure development. It establishes best practices for implementing declarative logic and managing shared state through the use of persistent data structures and atomic references. The guide covers standards for documenting public APIs and organizing project directories to ensure portable library distribution. It details the application of consistent formatting and naming rules to improve source code readability and team collaboration. The scope extends to idiomatic

Dhall is a type-safe configuration language designed to create programmable configuration files that are guaranteed to terminate. It is a non-Turing-complete language that uses a strict type system to ensure correctness and prevent infinite loops during evaluation. The project functions as a deterministic configuration engine and marshalling tool, converting programmable expressions into static formats such as JSON, YAML, and Bash. It distinguishes itself through a focus on security and integrity, using semantic hashing to pin remote imports and enforcing origin policies to prevent data exfil

Elsa Core is a workflow engine framework designed for defining, executing, and managing long-running business processes. It functions as a distributed workflow orchestrator and event-driven trigger system, capable of operating as a multi-tenant platform with secure data isolation. The project distinguishes itself through a flexible approach to workflow definitions, supporting a visual drag-and-drop designer, programmatic C# definitions, and portable JSON specifications. It provides a highly extensible architecture allowing for the development of custom activities and the use of a dynamic expr

This project is a compiler development tutorial that provides a series of guides and exercises for building a complete compiler from scratch. It focuses on the implementation of a structured compilation pipeline to transform high-level source code into executable machine instructions. The project covers the creation of a machine code generator for specific processor architectures and a static analysis framework. This framework includes methodologies for implementing type checking and constant folding to verify logic correctness before the final execution phase. The instructional material enc

date-fns is a JavaScript date utility library providing a collection of pure functions for manipulating, formatting, and calculating dates and times. It serves as an immutable date manipulation library and a tool for time zone management, ensuring that date transformations are performed without modifying the original date objects. The library functions as a date formatting tool that converts date objects into human-readable strings using custom patterns and international locales. It includes a specific toolset for adjusting and calculating date representations across different geographical re