Enum inc::AST

pub enum AST {
    Nil,
    Number(i64),
    Boolean(bool),
    Char(u8),
    Identifier(String),
    List(Vec<AST>),
    Let {
        bindings: Vec<(String, AST)>,
        body: Vec<AST>,
    },
}

The LISP AST

The canonical type to represent lisp programs. The parser parses the input program to generate an AST. See tests for several examples.

Variants

NilNumber(i64)Boolean(bool)Char(u8)

A unicode char encoded in UTF-8 can take upto 4 bytes and won't fit in a word; so this implementation makes sense only for ASCII.

Identifier(String)List(Vec<AST>)

Since Rust needs to know the size of the AST type upfront, we need an indirection here with Vec<> for recursive types. In this context, Vec is just a convenient way to have a Box<[AST]>

Let

Fields of Let

bindings: Vec<(String, AST)>body: Vec<AST>

Trait Implementations

impl PartialEq<AST> for AST

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

This method tests for self and other values to be equal, and is used by ==.

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

This method tests for !=.

impl From<i64> for AST

Idiomatic type conversions from the primitive types to AST

https://doc.rust-lang.org/rust-by-example/conversion/from_into.html https://ricardomartins.cc/2016/08/03/convenient_and_idiomatic_conversions_in_rust

fn from(i: i64) -> Self

Performs the conversion.

impl From<bool> for AST

fn from(b: bool) -> Self

Performs the conversion.

impl From<char> for AST

fn from(c: char) -> Self

Performs the conversion.

impl<'_> From<&'_ str> for AST

fn from(i: &str) -> Self

Performs the conversion.

impl Debug for AST

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

Formats the value using the given formatter.

impl FromStr for AST

Parse the input from user into the form the top level of the compiler understands.

type Err = Error

The associated error which can be returned from parsing.

fn from_str(program: &str) -> Result<Self, Error>

Parses a string s to return a value of this type.