## Description

`type2` is a slow, but versatile parser for context free languages (type 2 in the Chomsky hierarchy).

Being fed with a JSON file, specifying the language and a string via `stdin`, it decomposes the input, analyzes it and spits out its corresponding abstract syntax tree on `stdout`.

A typical call looks like this: `type2 language.tp2.json < input.txt`


## Language specification

A language is specified by a JSON file containing a value of the following type:

```
record<
	lexer_rules:list<
		record<
			type:string,
			parameters:map<string,any>
		>
	>,
	parser_rules:list<
		record<
			label:string,
			premise:string,
			conclusion:list<
				record<
					type:string,
					parameters:map<string,any>
				>
			>
		>
	>,
	parser_start:string
>
```

The recommended extension for such files is `.tp2.json`.


### Lexer rule types

| type | meaning | parameters |
|-- |-- |-- |
| `ignore` | disregard matching strings | `pattern` |
| `void` | do not assign a value to matching strings | `pattern`,`id` |
| `boolean` | interpret matching strings as boolean values | `pattern`,`id`,`value` |
| `int` | interpret matching strings as integer number values | `pattern`,`id` |
| `float` | interpret matching strings as floating point number values | `pattern`,`id` |
| `string` | interpret matching strings as string values | `pattern`,`id` |


### Conclusion element types

| type | meaning | parameters |
|-- |-- |-- |
| `terminal` | | `id` |
| `variable` | | `id` |