pest_extra

pest_extra provides additional functionality for the Pest parser

Features

Grammar

See below to find how to compile this grammar into Pest grammar.

Variables

A variable is a string that you can use in rules:

variable = "value" // easier than variable = { "value" }

Including other grammar in grammar

Idea: pest-parser/pest#759

Includes all the rules from one grammar to another.

Example

calculator.pest

include!("grammar2.pest")

integer = @{ ASCII_DIGIT+ }
primary = _{ integer | "(" ~ expr ~ ")" }
atom = _{ unary_minus? ~ primary }
expr = { atom ~ (bin_op ~ atom)* }
equation = _{ SOI ~ expr ~ EOI }

grammar2.pest

WHITESPACE = _{ " " }
unary_minus = { "-" }
bin_op = _{ add | subtract | multiply | divide | modulo }
	add = { "+" }
	subtract = { "-" }
	multiply = { "*" }
	divide = { "/" }
	modulo = { "%" }

compiled.pest

unary_minus =  { "-" }
divide      =  { "/" }
modulo      =  { "%" }
WHITESPACE  = _{ " " }
equation = _{ SOI ~ expr ~ EOI }
bin_op      = _{ add | subtract | multiply | divide | modulo }
atom     = _{ unary_minus? ~ primary }
integer  = @{ ASCII_DIGIT+ }
primary  = _{ integer | "(" ~ expr ~ ")" }
add         =  { "+" }
expr     =  { atom ~ (bin_op ~ atom)* }
multiply    =  { "*" }
subtract    =  { "-" }

Other

Installation (for formatting and minifying):

[dependencies]
pest_extra = { version = "0.1.0", features = [ "formatter" ] }

Formatting

Uses pest-fmt.

Usage:

use pest_extra::formatter;

fn main() {
    println!("{}", formatter::format(include_str!("./grammar.pest").to_string()));
}

Minifying

Minifies Pest grammar.

Usage:

use pest_extra::formatter;

fn main() {
    println!("{}", formatter::minify(include_str!("./grammar.pest").to_string()));
}

Comparsion:

calculator.pest

Size: 556 bytes

// No whitespace allowed between digits
integer = @{ ASCII_DIGIT+ }

unary_minus = { "-" }
primary = _{ integer | "(" ~ expr ~ ")" }
atom = _{ unary_minus? ~ primary }

bin_op = _{ add | subtract | multiply | divide | modulo }
	add = { "+" }
	subtract = { "-" }
	multiply = { "*" }
	divide = { "/" }
	modulo = { "%" }

expr = { atom ~ (bin_op ~ atom)* }

// We can't have SOI and EOI on expr directly, because it is used recursively (e.g. with parentheses)
equation = _{ SOI ~ expr ~ EOI }

WHITESPACE = _{ " " }

Size: 272 bytes (saved 48.92%)

minified-calculator.pest

integer=@{ASCII_DIGIT+}unary_minus={"-"}primary=_{integer|"("~expr~")"}atom=_{unary_minus?~primary}bin_op=_{add|subtract|multiply|divide|modulo}add={"+"}subtract={"-"}multiply={"*"}divide={"/"}modulo={"%"}expr={atom~(bin_op~atom)*}equation=_{SOI~expr~EOI}WHITESPACE=_{" "}

Compiling grammar into the Pest grammar

Installation

[dependencies]
pest_extra = "0.1.0"

Usage

use pest_extra::{
    formatter,
    parser::{compile_grammar, types::Grammar},
};

fn main() {
	// Compiling grammar
    if let Ok(grammar) = compile_grammar(Grammar::from_file("./grammar.pest").unwrap()) {
		// Formatting grammar
        println!("{}", formatter::format(grammar).unwrap());
    }
}

Pest VM

pest_extra has built-in pest_vm to create a parser from your grammar.

Installation

[dependencies]
pest_extra = { version = "0.1.0", features = [ "vm" ] }

Usage

use pest_extra::{
    parser::{compile_grammar, types::Grammar},
	vm
};

fn main() {
	// Compiling grammar
    if let Ok(grammar) = compile_grammar(Grammar::from_file("./grammar.pest").unwrap()) {
		// Creating parser
        let vm = vm::PestVm::new(&grammar).vm;
        let result = vm.parse("rule as &str", "input as &str");
    }
}

License

MIT