Contents

# basic parser that accepts only legal JSON
# parse-tree-nodes support "#evaluate" which returns the ruby-equivalent data-structure
require "babel_bridge"

class JsonParser < BabelBridge::Parser
  ignore_whitespace

  rule :document, any(:object, :array)

  rule :array, '[', many?(:value, ','), ']' do
    def evaluate; value.collect {|v| v.evaluate} end
  end

  rule :object, '{', many?(:pair,  ','), '}' do
    def evaluate; Hash[ pair.collect {|p| p.evaluate } ] end
  end

  rule :pair, :string, ':', :value do
    def evaluate; [ eval(string.to_s), value.evaluate ] end
  end

  rule :value, any(:object, :array, :ruby_compatible_literal, :null)

  rule :ruby_compatible_literal, any(:number, :string, :true, :false) do
    def evaluate; eval(to_s); end
  end

  rule :string, /"(?:[^"\\]|\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4}))*"/
  rule :number, /-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+-]?\d+)?/
  rule :true,   "true"
  rule :false,  "false"
  rule :null,   "null" do
    def evaluate; nil end
  end
end

BabelBridge::Shell.new(JsonParser.new).start

Version data entries

3 entries across 3 versions & 1 rubygems

Version	Path
babel_bridge-0.5.5	examples/json/json_parser2.rb
babel_bridge-0.5.4	examples/json/json_parser2.rb
babel_bridge-0.5.3	examples/json/json_parser2.rb