Awesome

Kacc

Yacc & Lex for Kinx.

Introduction

Kacc is an LALR(1) parser generator based on kmyacc. Moreover, a lexical analyzer is already included in this project. Therefore you can start developing a parser with a lexer very quickly.

Note that Kacc is published under MIT license, but kmyacc is licensed by GPLv2. Kacc is just including kmyacc as just a binary, so the license is separated.

Installation

Use kip to install Kacc because Kacc is provided as a package of Kinx.

$ kip install kacc

How To Use

Command Line

Use the kacc command with some options if necessary to generate your own parser.

$ kacc [-vltpod] parser.y

The generated parser will be outputted to the parser.kx file.
If you want to see the detail of a state, use -v to output the parser.output file.
If you want to debug it, use -t to make it be able to run with a debug mode.

Options

kacc has the following options.

Option	Meaning
`-v`	Generates the file of `parser.output` which contains human-readable parser tables and diagnostics.
`-l`	Does not insert #line control directives in `parser.kx`.
`-t`	Generates a debugging code.
`-p XX`	Uses `XX` rather than `Kacc` as a namespace of the parser.
`-o FILE`	`FILE` will be used as an output file instead of `parser.kx` which is by default.
`-d FILE`	`FILE` will be used instead of `parser.output`.

Example

The parser definition file is written in the same manner as the Yacc/Bison. This is an example of a calculator.

%{
using @kacc.Lexer;
%}

%token TOKEN_NUMBER TOKEN_IDENTIFIER

%left '+' '-'
%left '*' '/'

%%

start:    lines;

lines
    : line { $$ = $1; }
    | lines '\n' line { $$ = $3; }
    ;

line
    : assign  { $$ = $1; }
    | expr { $$ = $1; }
    | error { $$.value = "<error>"; }
    ;

assign
    : TOKEN_IDENTIFIER '=' expr { @setVar($1.value, $3.value); $$ = $3; }
    ;

expr
    : expr '+' expr { $$.value = $1.value + $3.value; }
    | expr '-' expr { $$.value = $1.value - $3.value; }
    | expr '*' expr { $$.value = $1.value * $3.value; }
    | expr '/' expr { $$.value = $1.value / $3.value; }
    | '(' expr ')' { $$ = $2; }
    | TOKEN_NUMBER { $$ = $1; }
    | TOKEN_IDENTIFIER { $$.value = @getVar($1.value); }
    ;

%%

/* Lexical analyzer */
var lexer = new Kacc.Lexer();
lexer.addSkip(/[ \t\r]+/);
lexer.addRule(/[_a-zA-Z][_a-zA-Z0-9]*/, TOKEN_IDENTIFIER);
lexer.addRule(/[0-9]+/, TOKEN_NUMBER) { &(value) => Integer.parseInt(value) };

/* Parser */
var vars = {};
var parser = new Kacc.Parser(lexer, {
    yyerror: &(msg)         => System.println(("ERROR! " + msg).red().bold()),
    setVar:  &(name, value) => vars[name] = value,
    getVar:  &(name)        => vars[name],
});

/* Calculation */
parser.parse("2 + 3 * 5") {
    System.println(_1.value);   // => 17
};

License

Kacc is published under MIT license.

Note that the kmyacc included in kacc as a binary module is published under GPLv2 license. See details for https://github.com/Kray-G/kmyacc.