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>,
    },
    Ref {
        inner: Box<Expr>,
    },
    Deref {
        inner: Box<Expr>,
    },
    Assign {
        target: Box<Expr>,
        value: Box<Expr>,
    },
    Seq {
        first: Box<Expr>,
        second: Box<Expr>,
    },
}

The abstract syntax tree.

Variants

Var(VarName)

Variable reference.

Lam

Lambda abstraction.

Fields

param: VarName

Bound parameter name.

body: Box<Expr>

Function body.

App

Function application (left-associative at the surface).

Fields

func: Box<Expr>

The function being applied.

arg: Box<Expr>

The argument.

Let

Let-binding.

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.

Fields

name: VarName

The name bound to the fixed point inside body.

body: Box<Expr>

The expression being closed over its own name.

Ref

Allocate a fresh cell initialised with the value of inner.

Fields

inner: Box<Expr>

The expression whose value will populate the new cell.

Deref

Dereference the cell pointed to by inner.

Fields

inner: Box<Expr>

The expression that must evaluate to a Value::Ref.

Assign

Assign value into the cell pointed to by target.

Fields

target: Box<Expr>

The expression that must evaluate to a Value::Ref.

value: Box<Expr>

The value to store.

Seq

Sequence: evaluate first (discarding its value), then evaluate second and return its value.

Fields

first: Box<Expr>

The expression evaluated for effect only.

second: Box<Expr>

The expression whose value is the result of the sequence.

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.

pub fn alloc(inner: Self) -> Self

Build a ref allocation node. Named alloc to avoid the ref keyword.

pub fn deref(inner: Self) -> Self

Build a dereference node.

pub fn assign(target: Self, value: Self) -> Self

Build an assignment node.

pub fn seq(first: Self, second: Self) -> Self

Build a sequence node.

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 PartialEq for Expr

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Eq for Expr

impl StructuralPartialEq for Expr