Class: EBNF::Base

Inherits:
Object
  • Object
show all
Includes:
BNF, LL1, Native, PEG
Defined in:
lib/ebnf/base.rb

Instance Attribute Summary collapse

Attributes included from LL1

#branch, #cleanup, #first, #follow, #pass, #start, #terminals

Instance Method Summary collapse

Methods included from PEG

#make_peg, #to_ruby_peg

Methods included from Native

#alt, #diff, #eachRule, #expression, #postfix, #primary, #ruleParts, #seq, #terminal

Methods included from LL1

#build_tables, #first_follow, #outputTable, #to_ruby_ll1

Methods included from BNF

#make_bnf

Constructor Details

#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

Instance Attribute Details

#astArray<Rule> (readonly)

Abstract syntax tree from parse

Returns:


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# File 'lib/ebnf/base.rb', line 93

def ast
  @ast
end

#errorsArray<String>

Grammar errors, or errors found genering parse tables

Returns:

  • (Array<String>)

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# File 'lib/ebnf/base.rb', line 98

def errors
  @errors
end

Instance Method Details

#debug(node, message) ⇒ Object #debug(message) ⇒ Object

Progress output when debugging

Overloads:

  • #debug(node, message) ⇒ Object

    Parameters:

    • node (String)

      relative location in input

    • message (String)

      (“”)

  • #debug(message) ⇒ Object

    Parameters:

    • message (String)

      (“”)

Yield Returns:

  • (String)

    added to message


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# File 'lib/ebnf/base.rb', line 344

def debug(*args, **options)
  return unless @options[:debug]
  depth = options[:depth] || @depth
  args << yield if block_given?
  message = "#{args.join(': ')}"
  str = "[#{@lineno}]#{' ' * depth}#{message}"
  @options[:debug] << str if @options[:debug].is_a?(Array)
  $stderr.puts(str) if @options[:debug] == true
end

#depthObject


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# File 'lib/ebnf/base.rb', line 304

def depth
  @depth += 1
  ret = yield
  @depth -= 1
  ret
end

#dupObject


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# File 'lib/ebnf/base.rb', line 290

def dup
  new_obj = super
  new_obj.instance_variable_set(:@ast, @ast.dup)
  new_obj
end

#each(kind) {|rule| ... } ⇒ Object

Iterate over each rule or terminal, except empty

Parameters:

  • kind (:termina, :rule)

Yields:

  • rule

Yield Parameters:


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# File 'lib/ebnf/base.rb', line 198

def each(kind, &block)
  ast.each {|r| block.call(r) if r.kind == kind && r.sym != :_empty}
end

#error(*args, **options) ⇒ Object

Error output


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# File 'lib/ebnf/base.rb', line 323

def error(*args, **options)
  depth = options[:depth] || @depth
  args << yield if block_given?
  message = "#{args.join(': ')}"
  @errors << message
  str = "[#{@lineno}]#{' ' * depth}#{message}"
  @options[:debug] << str if @options[:debug].is_a?(Array)
  $stderr.puts(str)
end

#find_rule(sym) ⇒ Rule

Find a rule given a symbol

Parameters:

  • sym (Symbol)

Returns:


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# File 'lib/ebnf/base.rb', line 300

def find_rule(sym)
  (@find ||= {})[sym] ||= ast.detect {|r| r.sym == sym}
end

#progress(*args, **options) ⇒ Object

Progress output, less than debugging


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# File 'lib/ebnf/base.rb', line 312

def progress(*args, **options)
  return unless @options[:progress] || @options[:debug]
  depth = options[:depth] || @depth
  args << yield if block_given?
  message = "#{args.join(': ')}"
  str = "[#{@lineno}]#{' ' * depth}#{message}"
  @options[:debug] << str if @options[:debug].is_a?(Array)
  $stderr.puts(str) if @options[:progress] || @options[:debug] == true
end

#renumber!Object

Renumber, rule identifiers


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# File 'lib/ebnf/base.rb', line 260

def renumber!
  ast.each_with_index do |rule, index|
    rule.id = (index + 1).to_s
  end
end

#to_html(format: :ebnf, validate: false) ⇒ String

Output formatted EBNF as HTML

Parameters:

  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf)

    (:ebnf)

  • validate (Boolean) (defaults to: false)

    (false) validate generated HTML.

Returns:

  • (String)

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# File 'lib/ebnf/base.rb', line 225

def to_html(format: :ebnf, validate: false)
  Writer.html(*ast, format: format, validate: validate)
end

#to_ruby(output = $stdout, grammarFile: nil, mod_name: 'Meta', **options) ⇒ Object

Output Ruby parser files

Parameters:

  • output (IO, StringIO) (defaults to: $stdout)
  • grammarFile (String) (defaults to: nil)
  • mod_name (String) (defaults to: 'Meta')

    ('Meta')


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# File 'lib/ebnf/base.rb', line 235

def to_ruby(output = $stdout, grammarFile: nil, mod_name: 'Meta', **options)
  unless output == $stdout
    output.puts "# This file is automatically generated by ebnf version #{EBNF::VERSION}"
    output.puts "# Derived from #{grammarFile}" if grammarFile
    unless self.errors.empty?
      output.puts "# Note, grammar has errors, may need to be resolved manually:"
      #output.puts "#   #{pp.conflicts.map{|c| c.join("\n#      ")}.join("\n#   ")}"
    end
    output.puts "module #{mod_name}"
    output.puts "  START = #{self.start.inspect}\n" if self.start
  end

  # Either output LL(1) BRANCH tables or rules for PEG parsing
  if ast.first.first
    to_ruby_ll1(output)
  else
    to_ruby_peg(output)
  end
  unless output == $stdout
    output.puts "end"
  end
end

#to_s(format: :ebnf) ⇒ String

Output formatted EBNF

Parameters:

  • format (:abnf, :ebnf, :isoebnf) (defaults to: :ebnf)

    (:ebnf)

Returns:

  • (String)

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# File 'lib/ebnf/base.rb', line 215

def to_s(format: :ebnf)
  Writer.string(*ast, format: format)
end

#to_sxpString

Write out parsed syntax string as an S-Expression

Returns:

  • (String)

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# File 'lib/ebnf/base.rb', line 205

def to_sxp
  require 'sxp' unless defined?(SXP)
  SXP::Generator.string(ast.map(&:for_sxp))
end

#to_ttl(prefix = nil, ns = "http://example.org/") ⇒ String

Write out syntax tree as Turtle

Parameters:

  • prefix (String) (defaults to: nil)

    for language

  • ns (String) (defaults to: "http://example.org/")

    URI for language

Returns:

  • (String)

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# File 'lib/ebnf/base.rb', line 271

def to_ttl(prefix = nil, ns = "http://example.org/")
  unless ast.empty?
    [
      "@prefix dc: <http://purl.org/dc/terms/>.",
      "@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>.",
      "@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.",
      ("@prefix #{prefix}: <#{ns}>." if prefix),
      "@prefix : <#{ns}>.",
      "@prefix re: <http://www.w3.org/2000/10/swap/grammar/regex#>.",
      "@prefix g: <http://www.w3.org/2000/10/swap/grammar/ebnf#>.",
      "",
      ":language rdfs:isDefinedBy <>; g:start :#{ast.first.id}.",
      "",
    ].compact
  end.join("\n") +

  ast.map(&:to_ttl).join("\n")
end

#valid?Boolean

Is the grammar valid?

Uses `#validate!` and catches `RangeError`

Returns:

  • (Boolean)

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# File 'lib/ebnf/base.rb', line 187

def valid?
  validate!
  true
rescue SyntaxError
  false
end

#validate!Object

Validate the grammar.

Makes sure that rules reference either strings or other defined rules.

Raises:

  • (RangeError)

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# File 'lib/ebnf/base.rb', line 170

def validate!
  ast.each do |rule|
    begin
      rule.validate!(@ast)
    rescue SyntaxError => e
      error("In rule #{rule.sym}: #{e.message}")
    end
  end
  raise SyntaxError, errors.join("\n") unless errors.empty?
end