Enum Expr 

pub enum Expr {
    Var(VarName),
    Lam {
        param: VarName,
        body: Box<Expr>,
    },
    App {
        func: Box<Expr>,
        arg: Box<Expr>,
    },
    Let {
        name: VarName,
        value: Box<Expr>,
        body: Box<Expr>,
    },
    Fix {
        name: VarName,
        body: Box<Expr>,
    },
}

The abstract syntax tree for the lambda calculus dialect.

Variant fields are exposed for direct pattern matching; the AST is purely a data shape and carries no internal invariants beyond well- formedness produced by the parser.

Variants

Var(VarName)

Variable reference.

Lam

Lambda abstraction: \param. body.

Fields

param: VarName

Bound parameter name.

body: Box<Expr>

Function body.

App

Function application: func arg (left-associative at the surface).

Fields

func: Box<Expr>

The function being applied.

arg: Box<Expr>

The argument supplied to the function.

Let

Let-binding: let name = value in body.

Fields

name: VarName

The bound name.

value: Box<Expr>

The value being bound.

body: Box<Expr>

The body in which the binding is in scope.

Fix

Fixed-point binding: fix name. body, where name may refer to the whole expression inside body. Models recursion without mutation.

Fields

name: VarName

The name bound to the fixed point inside body.

body: Box<Expr>

The expression being closed over its own name.

Implementations

impl Expr

pub fn var(name: impl Into<VarName>) -> Self

Build a variable reference.

pub fn lam(param: impl Into<VarName>, body: Self) -> Self

Build a lambda abstraction.

pub fn app(func: Self, arg: Self) -> Self

Build an application node.

pub fn bind(name: impl Into<VarName>, value: Self, body: Self) -> Self

Build a let-binding. Named bind because let is a keyword.

pub fn fix(name: impl Into<VarName>, body: Self) -> Self

Build a fixed-point binding.

Trait Implementations

impl Clone for Expr

fn clone(&self) -> Expr

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Expr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Display for Expr

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for Expr

impl PartialEq for Expr

fn eq(&self, other: &Expr) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for Expr