Class: EBNF::Base

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

Instance Attribute Summary collapse

Attributes included from LL1

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

Instance Method Summary collapse

Methods included from Parser

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

Methods included from LL1

#build_tables, #first_follow, #outputTable

Methods included from BNF

#make_bnf

Constructor Details

#initialize(input, 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)
  • options (Hash{Symbol => Object}) (defaults to: {})

Options Hash (options):

  • :debug (Boolean, Array) —

    Output debug information to an array or STDOUT.

  • :format (Symbol) — default: :ebnf —

    Format of input, one of :ebnf, or :sxp



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# File 'lib/ebnf/base.rb', line 124

def initialize(input, options = {})
  @options = {:format => :ebnf}.merge(options)
  @lineno, @depth, @errors = 1, 0, []
  terminal = false
  @ast = []

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

  case @options[:format]
  when :sxp
    require 'sxp' unless defined?(SXP)
    @ast = SXP::Reader::Basic.read(input).map {|e| Rule.from_sxp(e)}
  when :ebnf
    scanner = StringScanner.new(input)

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

        rule.kind = :terminal if terminal # Override after we've parsed @terminals
        rule.orig = r
        @ast << rule
      end
    end
  else
    raise "unknown input format #{options[:format].inspect}"
  end
end

Instance Attribute Details

#ast ⇒ Array<Rule> (readonly)

Abstract syntax tree from parse

Returns:



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# File 'lib/ebnf/base.rb', line 108

def ast
  @ast
end

#errors ⇒ Array<String>

Grammar errors, or errors found genering parse tables

Returns:

  • (Array<String>) 


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# File 'lib/ebnf/base.rb', line 113

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 265

def debug(*args)
  return unless @options[:debug]
  options = args.last.is_a?(Hash) ? args.pop : {}
  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

#depth ⇒ Object 



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# File 'lib/ebnf/base.rb', line 223

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

#dup ⇒ Object 



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# File 'lib/ebnf/base.rb', line 186

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 167

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

#error(*args) ⇒ Object

Error output



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# File 'lib/ebnf/base.rb', line 243

def error(*args)
  options = args.last.is_a?(Hash) ? args.pop : {}
  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 196

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

#progress(*args) ⇒ Object

Progress output, less than debugging



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# File 'lib/ebnf/base.rb', line 231

def progress(*args)
  return unless @options[:progress] || @options[:debug]
  options = args.last.is_a?(Hash) ? args.pop : {}
  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

#to_s ⇒ String

Output formatted EBNF

Returns:

  • (String) 


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# File 'lib/ebnf/base.rb', line 182

def to_s
  Writer.string(*ast)
end

#to_sxp ⇒ String

Write out parsed syntax string as an S-Expression

Returns:

  • (String) 


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# File 'lib/ebnf/base.rb', line 174

def to_sxp
  require 'sxp' unless defined?(SXP)
  SXP::Generator.string(ast.sort_by{|r| r.id.to_f}.map(&:for_sxp))
end

#to_ttl(prefix, ns) ⇒ String

Write out syntax tree as Turtle

Parameters:

  • prefix (String) —

    for language

  • ns (String) —

    URI for language

Returns:

  • (String) 


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

def to_ttl(prefix, ns)
  unless ast.empty?
    [
      "@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}>.",
      "@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}.",
      "",
    ]
  end.join("\n") +

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