DenotationSemantic.rb

require_relative 'SmallstepSemantic'

class Number
  def to_ruby
    "-> e { #{value.inspect} }"
  end
end

class Boolean
  def to_ruby
    "-> e { #{value.inspect} }"
  end
end

class Variable
  def to_ruby
    "-> e { e[#{name.inspect}] }"
  end
end

class Add
  def to_ruby
    "-> e { (#{left.to_ruby}).call(e) + (#{right.to_ruby}).call(e) }"
  end
end

class Multiply
  def to_ruby
    "-> e { (#{left.to_ruby}).call(e) * (#{right.to_ruby}).call(e) }"
  end
end

class LessThan
  def to_ruby
    "-> e { (#{left.to_ruby}).call(e) < (#{right.to_ruby}).call(e) }"
  end
end

class Assign
  def to_ruby
    "-> e { e.merge({ #{name.inspect} => (#{expression.to_ruby}).call(e) }) }"
  end
end

class DoNothing
  def to_ruby
    "-> e { e }"
  end
end

class If
  def to_ruby
    "-> e {" +
        "if (#{condition.to_ruby}).call(e)" +
        " then (#{consequence.to_ruby}).call(e)" +
        " else (#{alternative.to_ruby}).call(e)" +
        " end }"
  end
end

class Sequence
  def to_ruby
    "-> e { (#{second.to_ruby}).call((#{first.to_ruby}).call(e)) }"
  end
end

class While
  def to_ruby
    "-> e {" +
        " while (#{condition.to_ruby}).call(e); e = (#{body.to_ruby}).call(e); end;" +
        " e " +
        " }"
  end
end

stmt = While.new(
    LessThan.new(Variable.new(:x), Number.new(5)),
    Assign.new(:x, Multiply.new(Variable.new(:x), Number.new(3)))
)
puts stmt.to_ruby
proc = eval(stmt.to_ruby)
puts proc.call({ :x => 1})