ruby 运行报错 uninitialized constant Sequence (NameError)。
看着《The Ruby Programing》这本书的例子自己写了2个类。
Sequence.rb

#
#this class represents a sequence of numbers characterized by the three
#parameters from, to, and by. The numbers x in the sequence obey the 
#following two constraints:
# 
#      from  <= x <= to
#      x = from + n*by, where n is aninteger
#
class Sequence
  #This is an enumerable class; it defines an each iterator below.
  #initialize newly created instances of the class
  def initialize(from, to, by)
    #Just save our paramerters into instance variables for later use
    @from, @to, @by = from, to, by #Note parallel assignmendt and @ prefix
  end
  
  #this is the iterator required by the Enumerable module
  def each
    x = @from   #Start at the starting point
    while x <= @to  #while we haven't reached the end
      yield x       #pass x to rhe block associated with the iterator
      x += @by      #Increment x
    end
  end
  
  #Define the length method (following arrarys) to return hte numgber of
  #values in the sequence
  def length
    return 0 if @from > @to
    Integet((@to - @from)/@by) + 1
  end
  
  #Define another name for the same method
  #It is common for methods to have multiple names in Ruby
  alias size length      #size is now a synonym for length
  #Override the array-access operator give random accesss to give random access to the sequence
  def[](index)
    return nil if index < 0 #Return nul for negative indexes
    v = @from + index*@by   #compute the value
    if v <= @to             #if it is part of the sequence
      v                     #return it
    else                    #otherwise
      nil
    end
  end
  
  #Override arichmetic operators to return new Squence objects 
 
  def *(factor)
    Squence.new(@from*factor, @to*facotor, @by*factor)
  end
  
  def +(offset)
    Squence.new(@from + offset, @to + offset, @by)
  end
end

Hello.rb

s = Sequence.new(1, 10, 2)    #from 1 to 10 by 2's
s.each {|x| print x}
print s[s.size - 1]
t = (s+1)*2

我使用的编译器是Apatana
两个类都是在一个目录下面的。
我是初学者使用ruby，请问是哪里出错了呢？谢谢！
[解决办法]
require "sequence"

是请求这个文件，

Sequence.rb #前面字母小写