1  # coding: utf-8
   2  # frozen_string_literal: true
   3 
   4 
   5 
   6  module Umu
   7 
   8  module Environment
   9 
  10  module Tracer
  11 
  12  module Stack
  13 
  14  class Abstract < Abstraction::Collection
  15      def each
  16          return self.to_enum unless block_given?
  17 
  18          elem = self
  19 
  20          until elem.kind_of? Empty
  21              yield elem.event
  22 
  23              elem = elem.old_cons
  24          end
  25 
  26          nil
  27      end
  28 
  29 
  30      def push(event)
  31          ASSERT.kind_of event, Tracer::Event
  32 
  33          Cons.new(event, self).freeze
  34      end
  35 
  36 
  37      def pop
  38          raise X::InternalSubclassResponsibility
  39      end
  40 
  41 
  42      def print
  43          self.each do |event|
  44              STDERR.puts event.to_s
  45          end
  46      end
  47  end
  48 
  49 
  50 
  51  class Empty < Abstract
  52      def pop
  53          ASSERT.abort "Empty Stack"
  54      end
  55  end
  56 
  57  EMPTY = Empty.new.freeze
  58 
  59 
  60  class Cons < Abstract
  61      attr_reader :event
  62      attr_reader :old_cons
  63 
  64 
  65      def initialize(event, old_cons)
  66          ASSERT.kind_of event,       Tracer::Event
  67          ASSERT.kind_of old_cons,    Abstract
  68 
  69          @event      = event
  70          @old_cons   = old_cons
  71      end
  72 
  73 
  74      def pop
  75          self.old_cons
  76      end
  77  end
  78 
  79 
  80 
  81  module_function
  82 
  83      def empty
  84          EMPTY
  85      end
  86  end # Umu::Environment::Tracer::Stack
  87 
  88  end # Umu::Environment::Tracer
  89 
  90  end # Umu::Environment
  91 
  92  end # Umu