85 lines
2.7 KiB
Markdown
85 lines
2.7 KiB
Markdown
# LEMON.JS - LALR(1) Parser Generator for JavaScript
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Lemon.JS is an LALR(1) parser generator for JavaScript based on Lemon parser generator for C included in SQLite package distribution.
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## Parser Code Base
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Files `lemon.c`, `lempar.c`, `lemon.html` are extracted from SQLite v3.17.0. Original parser generator code is slightly fixed to produce JavaScript compatible statements. Parser template translated from C to JavaScript. Source comments mostly not touched to keep it easy diff against original file.
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Both original C version and patched JS version are included for side by side comparison for reference.
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## Installation
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Compile lenon-js.c with any C compiler and place in anywhere with lempar.js side by side.
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## Compilation
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Prerequisites: C compiler, for example GCC.
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```bash
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gcc -o lemon-js -O2 lemon-js.c
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```
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## Usage
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```bash
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lemon-js <filename>.y
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```
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See http://www.hwaci.com/sw/lemon/lemon.html for more details.
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## Special Directives
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See lemon.html for additional documentation.
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- %name - Set parser class name (default is "Parse")
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- %include - Include code in the beginning of file (usefull for imports)
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- %code - Include code in the end of file (usefull for exports or main code)
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- %token_destructor - Define code which will be executed on token destruction.
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- %default_destructor
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- %token_prefix - Define token name prefix.
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- %syntax_error - Define custom error handler for syntax erorrs.
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- %parse_accept - Define handler for all accepted tokens.
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- %parse_failure - Define handler for parse errors.
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- %stack_overflow - Define handler for stack overflow.
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- %extra_argument - **NOT SUPPORTED**
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- %token_type - **NOT SUPPORTED**
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- %default_type - **NOT SUPPORTED**
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- %stack_size - Set default stack size.
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- %start_symbol
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- %left - Set left associative tokens.
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- %right - Set right associative tokens.
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- %nonassoc - Set non associative tokens.
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- %destructor - Define custom parser destructor.
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- %type - **NOT SUPPORTED**
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- %fallback - Define fallback logic for tokens.
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- %wildcard - Define WILDCARD token.
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- %token_class - **NOT SUPPORTED**
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Notes:
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- some expressions, for example, regular expression `/\*/` could break lemon parser in `%code` or `%include` sections.
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- the best place to put something like `module.exports = ParserName;` or `export default ParserName;` is in `%code` section.
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## TODO
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- add some tests for different options
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- document variables
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- YYNOERRORRECOVERY ?
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- YYERRORSYMBOL ?
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- rename methods, variables, get rid of YY prefixes?
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- enable asserts, could be usefull for testing
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## Alternative Lexers
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- https://github.com/tantaman/lexed.js
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- https://github.com/aaditmshah/lexer
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- https://github.com/YuhangGe/jslex
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## Alternative Parsers
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- https://github.com/sormy/flex-js
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- http://jscc.brobston.com
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- http://zaach.github.io/jison/
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- https://pegjs.org
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