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 # vartan
 
-vartan provides a compiler that generates a parsing table and a driver for golang.
+vartan provides a compiler that generates a SLR parsing table and a driver for golang.
 
 [![Test](https://github.com/nihei9/vartan/actions/workflows/test.yml/badge.svg?branch=main)](https://github.com/nihei9/vartan/actions/workflows/test.yml)
 
 ## Status
 
-Now Developing
+🚧 Now Developing
+
+## Installation
+
+```sh
+$ go install github.com/nihei9/vartan/cmd/vartan@latest
+```
+
+## Usage
+
+vartan uses BNF-like DSL to define your grammar. As an example, let's write a grammar that represents a simple expression.
+
+```
+expr
+    : expr add_op term
+    | term
+    ;
+term
+    : term mul_op factor
+    | factor
+    ;
+factor
+    : number
+	| id
+	;
+
+whitespaces: "[\u{0009}\u{0020}]+" #skip;
+number: "[0-9]+";
+id: "[A-Za-z_]+";
+add_op: '+';
+mul_op: '*';
+```
+
+Save the above grammar to a file in UTF-8. In this explanation, the file name is `expr.vr`.
+
+Next, generate a parsing table using `vartan compile` command.
+
+```sh
+$ vartan compile -g expr.vr -o expr.json
+```
+
+If you want to make sure that the grammar behaves as expected, you can use `vartan parse` command to try parse without implementing a driver.
+
+⚠️ An encoding that `vartan parse` command and the driver can handle is only UTF-8.
+
+```sh
+$ echo -n 'foo + bar * baz * 100 ' | vartan parse expr.json
+Accepted
+expr
+├─ expr
+│  └─ term
+│      └─ factor
+│          └─ id "foo"
+├─ add_op "+"
+└─ term
+    ├─ term
+    │  ├─ term
+    │  │  └─ factor
+    │  │      └─ id "bar"
+    │  ├─ mul_op "*"
+    │  └─ factor
+    │      └─ id "baz"
+    ├─ mul_op "*"
+    └─ factor
+        └─ number "100"
+```
+
+When `vartan parse` command successfully parses the input data, it prints a CST or an AST (if any).
+
+## Debug
+
+`vartan compile` command also generates a description file having `.desc` suffix along with a parsing table. This file describes each state in the parsing table in detail. If your grammar contains conflicts, see `Conflicts` section of this file.