Class: ShuntingYard::Interpreter

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Interpreter

Returns a new instance of Interpreter.



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# File 'lib/shunting_yard/interpreter.rb', line 6

def initialize
  @functions = []
  @operators = []
end

Instance Attribute Details

#functions ⇒ Object

Returns the value of attribute functions.



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# File 'lib/shunting_yard/interpreter.rb', line 3

def functions
  @functions
end

#operators ⇒ Object

Returns the value of attribute operators.



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# File 'lib/shunting_yard/interpreter.rb', line 4

def operators
  @operators
end

Instance Method Details

#add_function(*args) ⇒ Object 



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# File 'lib/shunting_yard/interpreter.rb', line 11

def add_function(*args)
  functions << Function.new(*args)
end

#add_operator(*args) ⇒ Object 



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# File 'lib/shunting_yard/interpreter.rb', line 15

def add_operator(*args)
  operators << Operator.new(*args)
end

#evaluate(rpn_tokens) ⇒ Object

Raises:



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# File 'lib/shunting_yard/interpreter.rb', line 73

def evaluate(rpn_tokens)
  rpn = rpn_tokens.dup
  stack = []

  while rpn.any?
    current = rpn.shift

    case current
    when Function, Operator
      arity = current.evaluator.arity
      raise InvalidArgumentsCountError if stack.size < arity

      operands = stack.pop(arity)
      stack << current.evaluator.(*operands)
    when Operand
      stack << current.value
    end
  end

  raise InvalidArgumentsCountError if stack.size > 1

  stack[0]
end

#to_rpn(source_tokens) ⇒ Object 



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# File 'lib/shunting_yard/interpreter.rb', line 19

def to_rpn(source_tokens)
  tokens = source_tokens.dup
  output = ReversePolishNotation.new
  op_stack = []

  while tokens.any?
    current = match_token(tokens.shift)

    case current
    when ArgumentSeparator
      while op_stack.any? &&
            op_stack.last.class != Parenthesis
        output << op_stack.pop
      end
    when Function
      op_stack << current
    when Parenthesis
      case current.side
      when :left
        op_stack << current
      when :right
        while op_stack.last.class != Parenthesis
          raise MismatchedParenthesesError if op_stack.empty?

          output << op_stack.pop
        end

        op_stack.pop
      end
    when Operand
      output << current
    when Operator
      while op_stack.any? &&
            op_stack.last.class != Parenthesis &&
            (op_stack.last.class == Function ||
              op_stack.last.precedence > current.precedence ||
              op_stack.last.precedence == current.precedence && current.associativity == :left)
        output << op_stack.pop
      end

      op_stack << current
    end
  end

  while op_stack.any?
    current = op_stack.pop
    raise MismatchedParenthesesError if current.class == Parenthesis

    output << current
  end

  output
end