class SXP::Reader::Scheme

A Scheme R4RS S-expressions parser.

@see people.csail.mit.edu/jaffer/r4rs_9.html#SEC65

Constants

CHARACTERS

Escape characters, used in the form `#newline`. Case is treated insensitively @see people.csail.mit.edu/jaffer/r4rs_9.html#SEC65

DECIMAL
INTEGER_BASE_10
INTEGER_BASE_16
INTEGER_BASE_2
INTEGER_BASE_8
RATIONAL

Public Class Methods

new(input, version: :r4rs, **options, &block) click to toggle source

Initializes the reader.

@param [IO, StringIO, String] input @param [Hash{Symbol => Object}] options @option options [Symbol] :version (:r4rs)

Calls superclass method SXP::Reader::new
# File lib/sxp/reader/scheme.rb, line 28
def initialize(input, version: :r4rs, **options, &block)
  super(input, version: version, **options, &block)
end

Public Instance Methods

read_atom() click to toggle source

@return [Object]

# File lib/sxp/reader/scheme.rb, line 43
def read_atom
  case buffer = read_literal
    when '.'             then buffer.to_sym
    when RATIONAL        then Rational($1.to_i, $2.to_i)
    when DECIMAL         then Float(buffer)
    when INTEGER_BASE_10 then Integer(buffer)
    else buffer.to_sym
  end
end
read_character() click to toggle source

Read characters sequences like `#space`. Otherwise, reads a single character. Requires the ability to put eroneously read characters back in the input stream

@return [String] @see people.csail.mit.edu/jaffer/r4rs_9.html#SEC65

# File lib/sxp/reader/scheme.rb, line 79
def read_character
  lit = read_literal

  return " " if lit.empty? && peek_char == " "
  CHARACTERS.fetch(lit.downcase) do
    # Return just the first character
    unread(lit[1..-1])
    lit[0,1]
  end
end
read_sharp() click to toggle source

@return [Object]

# File lib/sxp/reader/scheme.rb, line 55
def read_sharp
  skip_char # '#'
  case char = read_char
    when ?n, ?N  then nil    # not in Scheme per se
    when ?f, ?F  then false
    when ?t, ?T  then true
    when ?b, ?B  then read_integer(2)
    when ?o, ?O  then read_integer(8)
    when ?d, ?D  then read_integer(10)
    when ?x, ?X  then read_integer(16)
    when ?\\     then read_character
    when ?;      then skip; read
    when ?!      then skip_line; read # shebang
    else raise Error, "invalid sharp-sign read syntax: ##{char.chr}"
  end
end
read_token() click to toggle source

@return [Object]

Calls superclass method SXP::Reader::Extended#read_token
# File lib/sxp/reader/scheme.rb, line 34
def read_token
  case peek_char
    when ?# then [:atom, read_sharp]
    else super
  end
end