Class: LambdaGem::Expression

Inherits:
Object
  • Object
show all
Defined in:
lib/expression.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(expression = nil, order = :infix, dictionary = nil) ⇒ Expression

Returns a new instance of Expression.



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# File 'lib/expression.rb', line 8

def initialize expression=nil, order=:infix, dictionary=nil     
  order = :infix if !@@AVAILABLE_ORDERING.include? order
  @dictionary = Dictionary.new
  @formula, @current_order, @tree = expression, order, Tree.new
  tree_from_expression(expression,order) if !expression.nil?
end

Instance Attribute Details

#current_order ⇒ Object

Returns the value of attribute current_order.



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# File 'lib/expression.rb', line 6

def current_order
  @current_order
end

#dictionary ⇒ Object

Returns the value of attribute dictionary.



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# File 'lib/expression.rb', line 6

def dictionary
  @dictionary
end

#tree ⇒ Object

Returns the value of attribute tree.



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# File 'lib/expression.rb', line 6

def tree
  @tree
end

Instance Method Details

#evaluate ⇒ Object 



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# File 'lib/expression.rb', line 63

def evaluate
 eval(@tree.root)
end

#formula ⇒ Object 



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# File 'lib/expression.rb', line 15

def formula
 @formula
end

#formula=(new_expression) ⇒ Object 



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# File 'lib/expression.rb', line 19

def formula= new_expression
  tree_from_expression new_expression
  @formula = new_expression
end

#operator?(token) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/expression.rb', line 59

def operator?(token)
 @dictionary.contains?(token.to_s)
end

#tree_from_expression(expression = @formula, order = :infix) ⇒ Object 



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# File 'lib/expression.rb', line 24

def tree_from_expression expression=@formula, order=:infix
  tokens = tokenize expression
  operator_stack, node_stack = [], []

  tokens.each do |token|
    token = token.downcase

    if operator?(token)
      until(operator_stack.empty? or
            operator_stack.last.data == "(" or
            @dictionary.operator_priority[operator_stack.last.data] < @dictionary.operator_priority[token])
        pop_connect_push operator_stack, node_stack
      end
      operator_stack.push(Node.new(token))
    elsif token == "("
      operator_stack.push(Node.new(token))
    elsif token == ")"
      while operator_stack.last.data != "("
        pop_connect_push operator_stack, node_stack
      end
      operator_stack.pop #throw '('
    else
      node_stack.push(Node.new(token))
    end

  end

  until operator_stack.empty?
    pop_connect_push operator_stack, node_stack
  end

  @tree.root = node_stack.last
  @tree
end