mooncakes.io

marianoguerra/shrubbery/ast does not have a README file

Node

pub(all) struct Node {
  it : Shrub
  span : @marianoguerra/shrubbery/basic.Span
Span
  meta : @marianoguerra/shrubbery/raw.Meta
Meta
}

One node: what it is, where it came from, and how to write it back.

Node::canonical

source

fn Node::canonical(self : Node) -> String

The canonical text form, for comparing our parse against the reference's.

This is the S-expression the reference produces, written with @sexp's escaping so that both sides of the comparison are all-ASCII and an encoding difference in transit cannot look like a parse difference.

Node::children

source

fn Node::children(self : Node) -> Array[Node]

The children of a compound node, or an empty array for a leaf.

Node::new

source

fn Node::new(it : Shrub, span : @marianoguerra/shrubbery/basic.Span
Span, meta? : @marianoguerra/shrubbery/raw.Meta
Meta) -> Node

Node::to_source

source

fn Node::to_source(self : Node) -> String

The source text this node came from.

Node::write_canonical

source

fn Node::write_canonical(self : Node, buf : StringBuilder) -> Unit

Node::write_source

source

fn Node::write_source(self : Node, buf : StringBuilder) -> Unit

The source text this node came from, rebuilt from its metadata.

Emission order is the field order of @raw.Meta and is load-bearing -- prefix, inner prefix, raw, then children or opaque_content, then tail, inner suffix, suffix -- with opaque_raw superseding the middle three.

Shrub

source

pub(all) enum Shrub {
  Id(String)
  Kw(String)
  Op(String)
  Lit(@marianoguerra/shrubbery/sexp.Datum
Datum)
  Parsed(@marianoguerra/shrubbery/sexp.Datum
Datum)
  Group(Array[Node])
  Block(Array[Node])
  Alts(Array[Node])
  Parens(Array[Node])
  Brackets(Array[Node])
  Braces(Array[Node])
  Quotes(Array[Node])
  Multi(Array[Node])
}

A parsed shrubbery.

The shape mirrors the reference's S-expression representation exactly, because that representation IS the interface: it is what #{...} escapes speak, what the parse oracle compares, and what a language built on this notation will pattern-match. A more strongly typed tree -- one where a group's optional block and alternatives were separate fields, so that the grammar's two structural laws were unrepresentable rather than merely true -- was the alternative, and it would have made the parser port a translation rather than a transcription of a mutual recursion with fourteen threaded state fields. The laws are stated below and checked by the oracle instead.

The laws, for the record:

Block appears only as the last item of a Group, or as the second-to-last with Alts after it.
Alts appears only as the last item of a Group, and contains only Blocks.
A Group is never empty.