PEG.js grammar for Fifth

fifth.peg

// Paste this into https://pegjs.org/online

Program = _ ts: TermSequence {
  return ts
}

TermSequence = terms: Term* _ {
  return terms
}

Term = _ t: (Number / Name / String / List / Map) {
  return t
}

Number = head: [1-9] tail: [0-9]* {
  return parseInt(head + tail.join(""))
}

Name = head: [a-z-<>=+*/-] tail: [0-9a-z<>=+*/-]* {
  return ":" + head + tail.join("")
}

String = '"' chars: (Nonquote / EscapedQuote)* '"' {
  return "$" + chars.join("")
}

Nonquote = [^"]

EscapedQuote = '""' {
  return '"'
}

List = '[' items: TermSequence ']' {
  return items
}

Map = '{' pairs: Pair* _ '}' {
  return {
    pairs
  }
}

Pair = a: Term b: Term {
  return [a, b]
}

_ = ([ \t\n\r] / Comment)*

Comment = "#" [^\n]* "\n"