7 releases (breaking)
0.6.1 | Jun 23, 2019 |
---|---|
0.5.0 | Jun 14, 2019 |
0.4.1 | Jun 9, 2019 |
0.3.0 | Jun 9, 2019 |
0.1.0 | Jun 2, 2019 |
#921 in WebAssembly
360KB
888 lines
λ-calculus Parser (using LALRPOP)
Write lambda calculus with ease, and evaluate it. There are a number of ways to use this library (each interchangeable with another):
Expression
AST variantsAbs
,App
, andVar
- Macros
abs!
/λ!
,app!
/γ!
, andvar!
- Parsed λ-calculus strings
λx.x (\a.\b.a)
- Native types:
u64
,bool
,fn
(WIP)
let id = λ!{x.x};
let one = λ!{f.λ!{x.γ!(f,x)}};
println!("{}", one.normalize(false));
assert_eq!(1u64, u64::from(app!({id},{one})));
Usage (JS)
import("./node_modules/lalrpop-lambda/lalrpop_lambda.js").then(lambda => {
console.log([
new lambda.Exp("x"),
new lambda.Exp(5),
new lambda.Exp(false),
new lambda.Exp("(\\x.x) y").normalize(true)
])
});
Usage (Rust)
use lalrpop_lambda::lambda::ExpressionParser;
let parser = ExpressionParser::new();
// Parse a single free variable.
let x = parser.parse("x");
// Parse the identity function.
let id = parser.parse(r"\x.x");
// f ∘ g
let compose = parser.parse(r"\f.\g.\x.(f (g x))"));
// Print the free variable in this expression.
let unbound_y = parser.parse(r"\x.x y");
println!("{}", unbound_y.free_variables());
// No need for parsing strings at all.
let id = λ!{x.x};
let one = λ!{f.λ!{x.γ!(f, x)}};
// Identity application.
let id = λ!{x.x};
println!("(id one): {} -> {}",
app!({&id}, {&one}),
app!({&id}, {&one}).normalize(false));
// Make the Y combinator.
let ω = parser.parse(r"λx.(x x)");
let Ω = parser.parse(r"(λx.(x x)) (λx.(x x))");
let W = parser.parse(r"λf.λx. f x x");
let Y = parser.parse(r"λf.(λx.f (x x)) (λx.f (x x))");
Development
This assumes you have an updated and working copy of [rustup
][rustup].
cargo +nightly [build | test | bench | doc | run --example <>]
WASM
First make sure you have wasm-pack
installed. Then:
wasm-pack build
Dependencies
~3.5–5MB
~108K SLoC