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POOptimal Design of a Ruby Data Structures Library
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  1. POOptimal Design of a Ruby Data Structures Library
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    copied!<p>I am working with data structures fundamentals in Ruby for learning at the CS sophomore/junior level. </p> <p>My question: Given the following code, does anyone see any design issues with this approach to a data structures library in Ruby? Especially the Module#abstract_method. Is it okay to do this in terms of duck typing philosophy? Does this make the code clearer for people from static languages and give some semblance of an interface?</p> <pre><code>class Module def abstract_method(symbol) module_eval &lt;&lt;-"end_eval" def #{symbol.id2name}(*args) raise MethodNotImplementedError end end_eval end end class AbstractObject &lt; Object abstract_method :compare_to protected :compare_to class MethodNotImplementedError &lt; StandardError; end def initialize super end include Comparable def &lt;=&gt;(other) if is_a?(other.class) return compare_to(other) elsif other.is_a?(self.class) return -other.compare_to(self) else return self.class &lt;=&gt; other.class end end end # methods for insertion/deletion should be provided by concrete implementations as this behavior # is unique to the type of data structure. Also, concrete classes should override purge to discard # all the contents of the container class Container &lt; AbstractObject include Enumerable def initialize super @count = 0 end attr_reader :count alias :size :count # should return an iterator abstract_method :iter # depends on iterator object returned from iter method # layer of abstraction for how to iterate a structure def each i = iter while i.more? yield i.succ end end # a visitor provides another layer of abstraction for additional # extensible and re-usable traversal operations def accept(visitor) raise ArgumentError, "Argument must be a visitor" unless visitor.is_a?(Visitor) each do |obj| break if visitor.done? visitor.visit(obj) end end # expected to over-ride this in derived classes to clear container def purge @count = 0 end def empty? count == 0 end def full? false end def to_s s = "" each do |obj| s &lt;&lt; ", " if not s.empty? s &lt;&lt; obj.to_s end self.class + "{" + s + "}" end end class List &lt; Container def initialize super end def compare_to(obj) "fix me" end end </code></pre>
 

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