Creating Custom Programming Languages

Grammar: A Comprehensive Overview of a Tree Language for Creating New Programming Languages

Introduction

In the world of programming, language design plays a pivotal role in shaping how developers interact with computers and express algorithms. While most programming languages adhere to traditional syntaxes, some innovators have sought to break free from conventional paradigms to create languages that are more intuitive, flexible, or even visually structured. One such innovation is Grammar, a unique language designed to facilitate the creation of new languages through a simple, tree-based structure.

Grammar, developed by Breck Yunits, emerged in 2017 with the primary goal of enabling programmers to define their own languages using a notation system based on trees. This article explores the features, capabilities, and applications of Grammar, along with an in-depth look at how it can be used to create new programming languages, complete with a parser, type checker, syntax highlighting, autocomplete, compiler, and interpreter.

What is Grammar?

Grammar is not just a tool for defining new syntaxes but a full-fledged language in its own right, designed to support the construction of tree-based programming languages. The central idea behind Grammar is its use of tree notation (or tree structures) to define the syntactic rules and semantics of new programming languages. This feature allows for a high degree of flexibility and abstraction, providing a robust foundation for the creation of languages with diverse characteristics.

At its core, Grammar allows users to:

Define new programming languages using simple tree-like structures.
Automatically generate tools such as parsers, type checkers, and compilers based on the defined grammar.
Integrate features like autocomplete, syntax highlighting, and error checking into the language development process.
Leverage both prefix and postfix notation for language features, allowing for versatile and efficient language design.

The Key Features of Grammar

Grammar’s appeal lies in the combination of simplicity and power. By focusing on tree-based syntax and leveraging modern programming concepts, it facilitates the creation of new languages that can meet the specific needs of developers. Here’s a detailed look at some of the key features and advantages that Grammar offers:

Tree Notation: The most distinctive feature of Grammar is its use of tree notation for defining the structure of programming languages. This notation represents syntactic rules in a way that is both human-readable and machine-friendly. Trees are often a natural way of representing hierarchical structures, and Grammar exploits this by modeling language constructs as nodes in a tree, with each node corresponding to a different language element.
Automatic Parser Generation: Grammar automatically generates parsers for any new language you create. A parser reads the source code written in the new language and interprets its structure according to the grammar you’ve defined. This automatic generation of a parser reduces the complexity of language development, making it much easier to define and experiment with new languages.
Type Checking: With Grammar, you can define rules for type checking, ensuring that programs written in your new language are semantically valid. This feature ensures that variables, functions, and expressions in your language adhere to the rules you’ve set, reducing runtime errors and improving code reliability.
Syntax Highlighting and Autocomplete: The development environment for Grammar integrates with modern IDEs and text editors to offer features like syntax highlighting and autocomplete. These features make working with your custom language more intuitive and less error-prone, providing immediate feedback and suggestions as you type.
Compiler and Interpreter: Grammar doesn’t stop at just defining a language—it also provides the tools necessary to run the code written in that language. The compiler translates your custom language code into executable code, while the interpreter allows you to run code directly without compiling. This functionality supports rapid prototyping and testing of new language features.
Postfix and Prefix Notation: Grammar supports both postfix and prefix language features. These notations are alternative ways of writing expressions, and each has its own benefits. Prefix notation places operators before their operands (e.g., + 3 5), while postfix notation places operators after their operands (e.g., 3 5 +). Both styles have advantages depending on the context, and Grammar allows for the creation of languages that can incorporate either or both notations seamlessly.
Open Source: Grammar is an open-source project, meaning that anyone can contribute to its development, improve it, or even use it as a basis for their own projects. This ensures a collaborative environment where the language evolves based on the needs and contributions of the community.
Support for Semantic Indentation: Although not universally supported in every case, Grammar’s structure can allow for semantic indentation, a feature that is increasingly popular in languages like Python. This means that the indentation of code can have semantic significance, such as indicating blocks of code or the scope of loops and conditionals.

How Grammar Works: The Basics of Creating a New Language

Creating a new programming language with Grammar involves defining the syntax and semantics of the language through a grammar file. This file contains the rules that describe the structure of the language. The process can be broken down into several steps:

Writing the Grammar File: The first step is to create the grammar file, which defines the structure of the new language. This file specifies the rules that determine how different language constructs should be parsed and interpreted. These rules are written using a tree-based notation, where each rule represents a node in the tree and its children represent the components that make up the construct.
Generating Tools: Once the grammar is defined, Grammar automatically generates several essential tools for the new language. These include:
- Parser: Converts source code into an abstract syntax tree (AST) based on the grammar.
- Type Checker: Ensures that all expressions and variables conform to the defined types.
- Compiler: Converts the source code into an executable format.
- Interpreter: Executes the code directly, without the need for compilation.
Testing the Language: With the grammar file and tools in place, you can begin writing programs in your new language. Grammar provides syntax highlighting, autocomplete, and error checking to help you debug and refine your language. The language can be tested and iterated upon rapidly, making it an excellent tool for prototyping new programming paradigms.
Extending the Language: Once the basic language is functional, Grammar allows you to add new features and extend the language’s capabilities. You can introduce new constructs, integrate additional syntax rules, and even adjust the parser to optimize the language’s performance or usability.

Applications of Grammar

The potential applications of Grammar are vast and varied, thanks to the flexibility and adaptability of the tree-based structure. Some of the key use cases for Grammar include:

Creating Domain-Specific Languages (DSLs): Many industries have specific needs that are not well-served by general-purpose programming languages. For example, the finance, healthcare, and gaming industries often require specialized languages for tasks like data analysis, simulations, and reporting. Grammar allows developers to easily create DSLs tailored to these specific needs, improving efficiency and clarity in specialized applications.
Educational Tools: Grammar can be used to create languages designed for teaching and learning programming concepts. By creating simplified languages that focus on specific aspects of programming (such as control flow, data structures, or algorithms), Grammar can be a powerful tool for education. Students can experiment with language creation and gain a deeper understanding of language design and theory.
Research and Prototyping: Researchers exploring new programming paradigms, algorithms, or computational theories can benefit from Grammar’s ability to quickly create and test new languages. The tool facilitates rapid prototyping and experimentation, making it easier to test hypotheses and iterate on ideas.
Creating Custom Scripting Languages: In many applications, developers need to embed a scripting language to allow users to write custom scripts. Grammar can be used to design and implement these custom scripting languages, giving users a way to interact with the application through a language that is specifically tailored to its functionality.
Language Comparison and Study: Grammar provides an excellent platform for comparing different programming paradigms, syntaxes, and semantics. Researchers and language designers can experiment with different combinations of features, such as using prefix vs. postfix notation, or integrating different ways of handling concurrency, error handling, and memory management.

Conclusion

Grammar represents a bold and innovative approach to programming language design. By combining the simplicity of tree-based notation with the power of modern programming tools, it empowers developers to create custom languages tailored to their specific needs. Whether for building domain-specific languages, teaching programming concepts, or prototyping new ideas, Grammar provides a flexible and robust framework for exploring the future of programming language design.

With its open-source nature, automatic generation of essential tools, and support for both prefix and postfix notation, Grammar is an invaluable resource for developers interested in pushing the boundaries of programming languages. By enabling rapid creation and iteration, it opens up new possibilities for how languages can be designed, developed, and deployed.