Class: ISOEBNFPegParser

Inherits:
Object
  • Object
show all
Includes:
EBNF::PEG::Parser
Defined in:
examples/isoebnf/parser.rb

Constant Summary collapse

TERMINAL_CHARACTER_BASE =

The base for terminal-character, which omits “‘”, ’“‘, and ’?‘. Could be more optimized, and one might quible with the overly-strictly defined character set, but it is correct.

%r{
  [a-zA-Z0-9] | # letter | decimal digit
  ,           | # concatenate symbol
  =           | # defining symbol
  [\|\/!]     | # definition separator symbol
  \*\)        | # end comment symbol
  \)          | # end group symbol
  \]          | # end option symbol
  \}          | # end repeat symbol
  \-          | # except symbol
  #\'          | # first quote symbol
  \*          | # repetition symbol
  #\"          | # second quote symbol
  #\?          | # special sequence symbol
  \(\*        | # start comment symbol
  \(          | # start group symbol
  \[          | # start option symbol
  \{          | # start repeat symbol
  [;\.]       | # terminator symbol
  [:+_%@&$<>^\x20\x23\\`~]  # other character
}x
TERMINAL_CHARACTER = 
%r{#{TERMINAL_CHARACTER_BASE}|['"\?]}
FIRST_TERMINAL_CHARACTER = 
%r{#{TERMINAL_CHARACTER_BASE}|["\?]}
SECOND_TERMINAL_CHARACTER = 
%r{#{TERMINAL_CHARACTER_BASE}|['\?]}
SPECIAL_SEQUENCE_CHARACTER = 
%r{#{TERMINAL_CHARACTER_BASE}|['"]}

Instance Attribute Summary collapse

Attributes included from EBNF::PEG::Parser

#packrat, #scanner, #whitespace

Instance Method Summary collapse

Methods included from EBNF::PEG::Parser

#clear_packrat, #debug, #depth, #error, #find_rule, #onFinish, #onStart, #onTerminal, #parse, #prod_data, #progress, #terminal_options, #terminal_regexp, #update_furthest_failure, #warn

Constructor Details

#initialize(input, **options, &block) ⇒ EBNFParser

Parser invocation.

On start, yield ourselves if a block is given, otherwise, return this parser instance

Parameters:

  • input (#read, #to_s)
  • options (Hash{Symbol => Object})

Options Hash (**options):

  • :level (Boolean) —

    Trace level. 0(debug), 1(info), 2(warn), 3(error).



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# File 'examples/isoebnf/parser.rb', line 201

def initialize(input, **options, &block)
  # If the `level` option is set, instantiate a logger for collecting trace information.
  if options.key?(:level)
    options[:logger] ||= Logger.new(STDERR).
      tap {|x| x.level = options[:level]}.
      tap {|x| x.formatter = lambda {|severity, datetime, progname, msg| "#{severity} #{msg}\n"}}
  end

  # Read input, if necessary, which will be used in a Scanner.
  @input = input.respond_to?(:read) ? input.read : input.to_s

  parsing_terminals = false
  @ast = []
  parse(@input,
         :syntax,
         ISOEBNFMeta::RULES,
         whitespace: %r{([\x09-\x0d\x20]|(?:\(\*(?:(?:\*[^\)])|[^*])*\*\)))+},
         **options
  ) do |context, *data|
    rule = case context
    when :rule
      # A rule which has already been turned into a `Rule` object.
      rule = data.first
      rule.kind = :terminal if parsing_terminals
      rule
    end
    @ast << rule if rule
  end
  @ast
end

Instance Attribute Details

#ast ⇒ Array<EBNF::Rule> (readonly)

Abstract syntax tree from parse

Returns:



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# File 'examples/isoebnf/parser.rb', line 48

def ast
  @ast
end

Instance Method Details

#to_sxp(**options) ⇒ String

Output formatted S-Expression of grammar

Returns:

  • (String) 


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# File 'examples/isoebnf/parser.rb', line 235

def to_sxp(**options)
  require 'sxp' unless defined?(SXP)
  # Output rules as a formatted S-Expression
  SXP::Generator.string(@ast.map(&:for_sxp))
end