Class: Abnf::Renderer

Inherits:
Object
  • Object
show all
Defined in:
../lib/abnf_renderer.rb

Overview

Abnf::Renderer renders the ABNF syntax tree from the Mapper::Grammar.

Class Method Summary (collapse)

Class Method Details

+ (Object) canonical(grammar)

If the grammar provided is the valid Mapper::Grammar instance, Renderer.canonical method returns the formatted ABNF text. 



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# File '../lib/abnf_renderer.rb', line 11

def Renderer.canonical grammar
  start = grammar.start_symbol
  res = ";start symbol is <#{start}>\n"
  symbols = grammar.symbols
  symbols.delete start
  symbols.unshift start
  symbols.each do |name|
    rule = grammar.fetch name
    rule.each do |alt|
      res += ( name + ' =' )
      res += '/' if alt != rule.first
      alt.each do |token|
        res += ' '
        case token.type
        when :literal
          res += ('"' + token.data.gsub(/\n/,'\\n') + '"')
        when :symbol
          res += token.data
        else
          raise "unsupported token.type=#{token.type}"
        end
      end
      res += "\n"
    end
    res += "\n"
  end
  res
end