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Tree-sitter CLI
===============
[![Build Status](https://travis-ci.org/tree-sitter/tree-sitter.svg?branch=master)](https://travis-ci.org/tree-sitter/tree-sitter)
[![Build status](https://ci.appveyor.com/api/projects/status/vtmbd6i92e97l55w/branch/master?svg=true)](https://ci.appveyor.com/project/maxbrunsfeld/tree-sitter/branch/master)
[![Crates.io](https://img.shields.io/crates/v/tree-sitter-cli.svg)](https://crates.io/crates/tree-sitter-cli)
The Tree-sitter CLI allows you to develop, test, and use Tree-sitter grammars from the command line. It works on MacOS, Linux, and Windows.
### Installation
You can install the `tree-sitter-cli` with `cargo`:
```sh
cargo install tree-sitter-cli
```
or with `npm`:
```sh
npm install tree-sitter-cli
```
You can also download a pre-built binary for your platform from [the releases page](https://github.com/tree-sitter/tree-sitter/releases/latest).
### Dependencies
The `tree-sitter` binary itself has no dependencies, but specific commands have dependencies that must be present at runtime:
* To generate a parser from a grammar, you must have [`node`](https://nodejs.org) on your PATH.
* To run and test parsers, you must have a C and C++ compiler on your system.
### Commands
* `generate` - The `tree-sitter generate` command will generate a Tree-sitter parser based on the grammar in the current working directory. See [the documentation](http://tree-sitter.github.io/tree-sitter/creating-parsers) for more information.
* `test` - The `tree-sitter test` command will run the unit tests for the Tree-sitter parser in the current working directory. See [the documentation](http://tree-sitter.github.io/tree-sitter/creating-parsers) for more information.
* `parse` - The `tree-sitter parse` command will parse a file (or list of file) using Tree-sitter parsers.

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# Implementation
Tree-sitter consists of two separate libraries, both of which expose C APIs.
Tree-sitter consists of two components: a C library (`libtree-sitter`), and a command-line tool (the `tree-sitter` CLI).
The first library, `libcompiler`, is
The library, `libtree-sitter`, is used in combination with the parsers
generated by the CLI, to produce syntax trees from source code and keep the
syntax trees up-to-date as the source code changes. `libtree-sitter` is designed to be embedded in applications. It is written in plain C. Its interface is specified in the header file [`tree_sitter/api.h`](https://github.com/tree-sitter/tree-sitter/blob/master/lib/include/tree_sitter/api.h).
The CLI is
used to generate a parser for a language by supplying a [context-free grammar](https://en.wikipedia.org/wiki/Context-free_grammar) describing the
language. `libcompiler` is a build tool; it is no longer needed once a parser has been generated. It is written in C++, but exposes a C interface, which is declared in the header file [`compiler.h`](https://github.com/tree-sitter/tree-sitter/blob/master/include/tree_sitter/compiler.h).
language. The CLI is a build tool; it is no longer needed once a parser has been generated. It is written in Rust, and is available on [crates.io](https://crates.io), [npm](http://npmjs.com), and as a pre-built binary [on GitHub](https://github.com/tree-sitter/tree-sitter/releases/latest).
The second library, `libruntime`, is used in combination with the parsers
generated by `libcompiler`, to produce syntax trees from source code and keep the
syntax trees up-to-date as the source code changes. `libruntime` is designed to be embedded in applications. It is written in plain C. Its interface is specified in the header file [`runtime.h`](https://github.com/tree-sitter/tree-sitter/blob/master/include/tree_sitter/runtime.h).
## The CLI
## The Compiler
The `libcompiler` library exports only one function: `ts_compile_grammar`. This function takes a context-free grammar as a JSON string and returns a parser as a string of C code. The source files in the [`src/compiler`](https://github.com/tree-sitter/tree-sitter/tree/master/src/compiler) directory all play a role in producing this C code. This section will describe some key parts of this process.
The `tree-sitter` CLI's most important feature is the `generate` subcommand. This subcommand reads context-free grammar from a file called `grammar.js` and outputs a parser as a C file called `parser.c`. The source files in the [`cli/src`](https://github.com/tree-sitter/tree-sitter/tree/master/cli/src) directory all play a role in producing the code in `parser.c`. This section will describe some key parts of this process.
### Parsing a Grammar
First, `libcompiler` must parse the JSON grammar. The format of the grammars is formally specified by the JSON schema in [grammar-schema.json](https://github.com/tree-sitter/tree-sitter/blob/master/src/compiler/grammar-schema.json). The parsing is implemented in [parser_grammar.cc](https://github.com/tree-sitter/tree-sitter/blob/master/src/compiler/parse_grammar.cc). It uses [udp/json-parser](https://github.com/udp/json-parser), one of Tree-sitter's few library dependencies.
First, Tree-sitter must must evaluate the JavaScript code in `grammar.js` and convert the grammar to a JSON format. It does this by shelling out to `node`. The format of the grammars is formally specified by the JSON schema in [grammar-schema.json](https://github.com/tree-sitter/tree-sitter/blob/master/cli/src/generate/grammar-schema.json). The parsing is implemented in [parse_grammar.rs](https://github.com/tree-sitter/tree-sitter/blob/master/cli/src/generate/parse_grammar.rs).
### Grammar Rules
A Tree-sitter grammar is composed of a set of *rules* - objects that describe how syntax nodes can be composed from other syntax nodes. There are several types of rules: symbols, strings, regexes, sequences, choices, repetitions, and a few others. Internally, these are all represented using a [tagged union](https://en.wikipedia.org/wiki/Tagged_union) class called [`Rule`](https://github.com/tree-sitter/tree-sitter/blob/master/src/compiler/rule.h). This class has a method called `match`, which makes it easy to [pattern-match](https://en.wikipedia.org/wiki/Pattern_matching) a rule, processing each type of rule with separate code.
A Tree-sitter grammar is composed of a set of *rules* - objects that describe how syntax nodes can be composed from other syntax nodes. There are several types of rules: symbols, strings, regexes, sequences, choices, repetitions, and a few others. Internally, these are all represented using an [enum](https://doc.rust-lang.org/book/ch06-01-defining-an-enum.html) called [`Rule`](https://github.com/tree-sitter/tree-sitter/blob/master/cli/src/generate/rules.rs).
### Preparing a Grammar
Once a grammar has been parsed, it must be transformed in several ways before it can be used to generate a parser. Each transformation is implemented by a separate file in the [`src/compiler/prepare_grammar`](https://github.com/tree-sitter/tree-sitter/tree/master/src/compiler/prepare_grammar) directory, and the transformations are ultimately composed together in `prepare_grammar.cc`.
Once a grammar has been parsed, it must be transformed in several ways before it can be used to generate a parser. Each transformation is implemented by a separate file in the [`prepare_grammar`](https://github.com/tree-sitter/tree-sitter/tree/master/cli/src/generate/prepare_grammar) directory, and the transformations are ultimately composed together in `prepare_grammar/mod.rs`.
At the end of these transformations, the initial grammar is split into two grammars: a *syntax grammar* and a *lexical grammar*. The syntax grammar describes how the language's [*non-terminal symbols*](https://en.wikipedia.org/wiki/Terminal_and_nonterminal_symbols) are constructed from other grammar symbols, and the lexical grammar describes how the grammar's *terminal symbols* (strings and regexes) can be composed from individual characters.

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@ -4,7 +4,7 @@ description = "Rust bindings to the Tree-sitter parsing library"
version = "0.3.5"
authors = ["Max Brunsfeld <maxbrunsfeld@gmail.com>"]
license = "MIT"
readme = "README.md"
readme = "binding/README.md"
keywords = ["incremental", "parsing"]
categories = ["api-bindings", "parsing", "text-editors"]

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Rust Tree-sitter
===========================
================
[![Build Status](https://travis-ci.org/tree-sitter/rust-tree-sitter.svg)](https://travis-ci.org/tree-sitter/rust-tree-sitter)
[![Build status](https://ci.appveyor.com/api/projects/status/d0f6vqq3rflxx3y6/branch/master?svg=true)](https://ci.appveyor.com/project/maxbrunsfeld/rust-tree-sitter/branch/master)
[![Build Status](https://travis-ci.org/tree-sitter/tree-sitter.svg?branch=master)](https://travis-ci.org/tree-sitter/tree-sitter)
[![Build status](https://ci.appveyor.com/api/projects/status/vtmbd6i92e97l55w/branch/master?svg=true)](https://ci.appveyor.com/project/maxbrunsfeld/tree-sitter/branch/master)
[![Crates.io](https://img.shields.io/crates/v/tree-sitter.svg)](https://crates.io/crates/tree-sitter)
Rust bindings to the [Tree-sitter][] parsing library.