61 lines
1.5 KiB
Markdown
61 lines
1.5 KiB
Markdown
## Description
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`type2` is a slow, but versatile parser for context free languages (type 2 in the Chomsky hierarchy).
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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`.
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A typical call looks like this: `type2 language.tp2.json < input.txt`
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## Language specification
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A language is specified by a JSON file containing a value of the following type:
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```
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record<
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lexer_rules:list<
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record<
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type:string,
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parameters:map<string,any>
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>
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>,
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parser_rules:list<
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record<
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label:string,
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premise:string,
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conclusion:list<
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record<
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type:string,
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parameters:map<string,any>
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>
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>
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>
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>,
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parser_start:string
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>
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```
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The recommended extension for such files is `.tp2.json`.
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### Lexer rule types
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| type | meaning | parameters |
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|-- |-- |-- |
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| `ignore` | disregard matching strings | `pattern` |
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| `void` | do not assign a value to matching strings | `pattern`,`id` |
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| `boolean` | interpret matching strings as boolean values | `pattern`,`id`,`value` |
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| `int` | interpret matching strings as integer number values | `pattern`,`id` |
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| `float` | interpret matching strings as floating point number values | `pattern`,`id` |
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| `string` | interpret matching strings as string values | `pattern`,`id` |
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### Conclusion element types
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| type | meaning | parameters |
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|-- |-- |-- |
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| `terminal` | | `id` |
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| `variable` | | `id` |
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