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测试文件

require 'ex48/parser.rb'
require "test/unit"

class TestParser < Test::Unit::TestCase

	def test_sentence()
		x = parse_sentence([['noun', 'bear'], ['verb', 'eat'], ['noun', 'honey']])
		
		assert_equal(x.subject, "bear")
		assert_equal(x.verb, "eat")
		assert_equal(x.object, "honey")
	end
	
	def test_player()
		x = parse_sentence([['verb', 'eat'], ['noun', 'honey']])
		
		assert_equal(x.subject, "player")
	end
	
	def test_subject()
		assert_raises(ParserError){parse_sentence([['noun', 'honey'], ['noun', 'honey']])}

	end
	
	def test_verb()
		assert_raises(ParserError){parse_sentence([['noun', 'bear'], ['noun', 'honey']])}

	end
	
	def test_object()
		assert_raises(ParserError){parse_sentence([['noun', 'bear'], ['verb', 'eat'],  ['verb', 'eat']])}

	end
end

程序文件

class ParserError < Exception
end

class Sentence

	def initialize(subject, verb, obj)
		# remember we take ['noun', 'princess'] pairs and convert them
		@subject = subject[1]
		@verb = verb[1]
		@object = obj[1]
	end
	
	attr_reader :subject
	attr_reader :verb
	attr_reader :object
end

def peek(word_list)
	if word_list
		word = word_list[0]
		return word[0]
	else
		retrun nil
	end
end

def match(word_list, expecting)
	if word_list
		word = word_list.shift
		
		if word[0] == expecting
			return word
		else
			return nil
		end
	else
		return nil
	end
end

def skip(word_list, word_type)
	while peek(word_list) == word_type
		match(word_list, word_type)
	end
end

def parse_verb(word_list)
	skip(word_list, 'stop')
	
	if peek(word_list) == 'verb'
		return match(word_list, 'verb')
	else
		raise ParserError.new("Expected a verb next.")
	end
end

def parse_object(word_list)
	skip(word_list, 'stop')
	next_word = peek(word_list)
	
	if next_word == 'noun'
		return match(word_list, 'noun')
	elsif next_word == 'direction'
		return match(word_list, 'direction')
	else
		raise ParserError.new("Expected a noun or direction next.")
	end
end

def parse_subject(word_list)
	skip(word_list, 'stop')
	next_word = peek(word_list)
	
	if next_word == 'noun'
		return match(word_list, 'noun')
	elsif next_word == 'verb'
		return ['noun', 'player']
	else
		raise ParserError.new("Expected a verb next.")
	end
end

def parse_sentence(word_list)
	subj = parse_subject(word_list)
	verb = parse_verb(word_list)
	obj = parse_object(word_list)
	
	return Sentence.new(subj, verb, obj)
end

LJZN

49创建句子

测试文件

程序文件

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