Class: RPN::Stack

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

Defined Under Namespace

Classes: InsufficientValuesAvailable, UnsolvableExpressionError

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(arity) ⇒ Stack

Returns a new instance of Stack.



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# File 'lib/rpn/stack.rb', line 8

def initialize arity
  @arity = arity
  @elements = []
end

Instance Attribute Details

#arity ⇒ Object (readonly)

Returns the value of attribute arity.



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# File 'lib/rpn/stack.rb', line 6

def arity
  @arity
end

#elements ⇒ Object (readonly)

Returns the value of attribute elements.



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# File 'lib/rpn/stack.rb', line 6

def elements
  @elements
end

Instance Method Details

#clear ⇒ Object 



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# File 'lib/rpn/stack.rb', line 44

def clear
  elements.clear
end

#pop(amount) ⇒ Object 



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# File 'lib/rpn/stack.rb', line 36

def pop amount
  elements.pop amount
end

#push(token) ⇒ Object 



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# File 'lib/rpn/stack.rb', line 32

def push token
  elements.push token
end

#size ⇒ Object 



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# File 'lib/rpn/stack.rb', line 40

def size
  elements.size
end

#solve(tokens) ⇒ Object

Raises:



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# File 'lib/rpn/stack.rb', line 13

def solve tokens
  clear
  tokens.each do |token|
    if Numeric === token
      push token
      next
    end
    raise InsufficientValuesAvailable\
          .new("Cannot apply #{token} to less than #{arity} values!") if size < arity
    result = pop(arity).inject do |acc, e|
      acc.send(token, e)
    end
    push result
  end
  raise UnsolvableExpressionError\
        .new("The final stack contained more than one value: #{elements.inspect}") if size > 1
  elements.first
end