Dust is a programming language and interactive shell. Dust can be used as a replacement for a traditional command line shell, as a scripting language and as a data format. Dust is fast, efficient and easy to learn.
Dust is an interpreted, general purpose language with first class functions. It is *data-oriented*, with extensive tools to manage structured and relational data. Dust also includes built-in tooling to import and export data in a variety of formats, including JSON, TOML, YAML and CSV.
Dust is an experimental project under active development. At this stage, features come and go and the API is always changing. It should not be considered for serious use yet.
You must have the default rust toolchain installed and up-to-date. Install [rustup] if it is not already installed. Run `cargo install dust-lang` then run `dust` to start the interactive shell. Use `dust --help` to see the full command line options.
To build from source, clone the repository and build the parser. To do so, enter the `tree-sitter-dust` directory and run `tree-sitter-generate`. In the project root, run `cargo run` to start the shell. To see other command line options, use `cargo run -- --help`.
Dust is at a very early development stage but performs strongly in preliminary benchmarks. The examples given were tested using [Hyperfine] on a single-core cloud instance with 1024 MB RAM. Each test was run 1000 times. The test script is shown below. Each test asks the program to read a JSON file and count the objects. The programs produced identical output with the exception that NodeJS printed in color.
For the first test, a file with four entries was used.
| Command | Mean [ms] | Min [ms] | Max [ms] | Relative |
Dust is formally defined as a Tree Sitter grammar in the tree-sitter-dust directory. Tree sitter generates a parser, written in C, from a set of rules defined in JavaScript. Dust itself is a rust binary that calls the C parser using FFI.
Tests are written in three places: in the Rust library, in Dust as examples and in the Tree Sitter test format. Generally, features are added by implementing and testing the syntax in the tree-sitter-dust repository, then writing library tests to evaluate the new syntax. Implementation tests run the Dust files in the "examples" directory and should be used to demonstrate and verify that features work together.
Tree Sitter generates a concrete syntax tree, which Dust traverses to create an abstract syntax tree that can run the Dust code. The CST generation is an extra step but it allows easy testing of the parser, defining the language in one file and makes the syntax easy to modify and expand. Because it uses Tree Sitter, developer-friendly features like syntax highlighting and code navigation are already available in any text editor that supports Tree Sitter.
Note that strings can be wrapped with any kind of quote: single, double or backticks. Numbers are always integers by default. Floats are declared by adding a decimal. If you divide integers or do any kind of math with a float, you will create a float value.
Lists are sequential collections. They can be built by grouping values with square brackets. Commas are optional. Values can be indexed by their position using dot notation with an integer. Dust lists are zero-indexed.
Maps are flexible collections with arbitrary key-value pairs, similar to JSON objects. A map is created with a pair of curly braces and its entries are variables declared inside those braces. Map contents can be accessed using dot notation.
Tables are strict collections, each row must have a value for each column. If a value is "missing" it should be set to an appropriate value for that type. For example, a string can be empty and a number can be set to zero. Dust table declarations consist of a list of column names, which are identifiers enclosed in pointed braces, followed by a list of rows.
The keywords `table` and `insert` make sure that all of the memory used to hold the rows is allocated at once, so it is good practice to group your rows together instead of using a call for each row.
Functions are first-class values in dust, so they are assigned to variables like any other value. The function body is wrapped in single parentheses. To create a function, use the "function" keyword. The function's arguments are identifiers inside of a set of pointed braces and the function body is enclosed in curly braces. To call a fuction, invoke its variable name inside a set of parentheses. You don't need commas when listing arguments and you don't need to add whitespace inside the function body but doing so may make your code easier to read.
In an **async** block, each statement is run in parallel. In this case, we want to read from a file and assign the data to a variable. It doesn't matter which statement finishes first, the last statement in the block will be used as the assigned value. If one of the statements in an **async** block produces an error, the other statements will stop running if they have not already finished.
