LEMON.JS - LALR(1) Parser Generator for JavaScript

Lemon.JS is an LALR(1) parser generator for JavaScript based on Lemon parser generator for C included in SQLite package distribution.

Parser Code Base

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.

Both original C version and patched JS version are included for side by side comparison for reference.

Installation

Compile lenon-js.c with any C compiler and place in anywhere with lempar.js side by side.

Compilation

Prerequisites: C compiler, for example GCC.

gcc -o lemon-js -O2 lemon-js.c

Usage

lemon-js <filename>.y

See http://www.hwaci.com/sw/lemon/lemon.html for more details.

Special Directives

See lemon.html for additional documentation.

• %name - Set parser class name (default is "Parse")
• %include - Include code in the beginning of file (usefull for imports)
• %code - Include code in the end of file (usefull for exports or main code)
• %token_destructor - Define code which will be executed on token destruction.
• %default_destructor
• %token_prefix - Define token name prefix.
• %syntax_error - Define custom error handler for syntax erorrs.
• %parse_accept - Define handler for all accepted tokens.
• %parse_failure - Define handler for parse errors.
• %stack_overflow - Define handler for stack overflow.
• %extra_argument - NOT SUPPORTED
• %token_type - NOT SUPPORTED
• %default_type - NOT SUPPORTED
• %stack_size - Set default stack size.
• %start_symbol
• %left - Set left associative tokens.
• %right - Set right associative tokens.
• %nonassoc - Set non associative tokens.
• %destructor - Define custom parser destructor.
• %type - NOT SUPPORTED
• %fallback - Define fallback logic for tokens.
• %wildcard - Define WILDCARD token.
• %token_class - NOT SUPPORTED

Notes:

• some expressions, for example, regular expression /\*/ could break lemon parser in %code or %include sections.
• the best place to put something like module.exports = ParserName; or export default ParserName; is in %code section.

TODO

• add some tests for different options
• document variables
• YYNOERRORRECOVERY ?
• YYERRORSYMBOL ?
• rename methods, variables, get rid of YY prefixes?
• enable asserts, could be usefull for testing

Alternative Lexers

• https://github.com/tantaman/lexed.js
• https://github.com/aaditmshah/lexer
• https://github.com/YuhangGe/jslex

Alternative Parsers

• https://github.com/sormy/flex-js
• http://jscc.brobston.com
• http://zaach.github.io/jison/
• https://pegjs.org