Method: EBNF::Base#initialize

Defined in:
lib/ebnf/base.rb

#initialize(input, format: :ebnf, **options) ⇒ Base

Parse the string or file input generating an abstract syntax tree in S-Expressions (similar to SPARQL SSE)

Parameters:

  • input (#read, #to_s)
  • format (Symbol) (defaults to: :ebnf) —

    (:ebnf) Format of input, one of ‘:abnf`, `:ebnf`, `:isoebnf`, `:isoebnf`, `:native`, or `:sxp`. Use `:native` for the native EBNF parser, rather than the PEG parser.

  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :debug (Boolean, Array) —

    Output debug information to an array or $stdout.

  • :validate (Boolean, Array) —

    Validate resulting grammar.



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# File 'lib/ebnf/base.rb', line 112

def initialize(input, format: :ebnf, **options)
  @options = options.dup
  @lineno, @depth, @errors = 1, 0, []
  @ast = []

  input = input.respond_to?(:read) ? input.read : input.to_s

  case format
  when :abnf
    abnf = ABNF.new(input, **options)
    @ast = abnf.ast
  when :ebnf
    ebnf = Parser.new(input, **options)
    @ast = ebnf.ast
  when :isoebnf
    iso = ISOEBNF.new(input, **options)
    @ast = iso.ast
  when :native
    terminals = false
    scanner = StringScanner.new(input)

    eachRule(scanner) do |r|
      debug("rule string") {r.inspect}
      case r
      when /^@terminals/
        # Switch mode to parsing terminals
        terminals = true
        rule = Rule.new(nil, nil, nil, kind: :terminals, ebnf: self)
        @ast << rule
      when /^@pass\s*(.*)$/m
        expr = expression($1).first
        rule = Rule.new(nil, nil, expr, kind: :pass, ebnf: self)
        rule.orig = expr
        @ast << rule
      else
        rule = depth {ruleParts(r)}

        rule.kind = :terminal if terminals # Override after we've parsed @terminals
        rule.orig = r
        @ast << rule
      end
    end
  when :sxp
    require 'sxp' unless defined?(SXP)
    @ast = SXP::Reader::Basic.read(input).map {|e| Rule.from_sxp(e)}
  else
    raise "unknown input format #{format.inspect}"
  end

  validate! if @options[:validate]
end