Class: LatexEval::PostfixNotation

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(notation) ⇒ PostfixNotation

Returns a new instance of PostfixNotation.



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# File 'lib/latex_eval/postfix_notation.rb', line 5

def initialize(notation)
  @notation = notation
  @operations = {
    add: {
      args: 2,
      operation: ->(a,b) { a + b },
    }, 
    subtract: {
      args: 2,
      operation: ->(a,b) { a - b },
    },
    multiply: {
      args: 2,
      operation: ->(a,b) { a * b },
    },
    divide: {
      args: 2, 
      operation: ->(a,b) { a / b },
    },
    power: {
      args: 2,
      operation: ->(a,b) { a ** b },
    },
    mod: {
      args: 2,
      operation: ->(a,b) { a % b },
    },
    negative: {
      args: 1,
      operation: ->(a) { -a },
    },
    positive: {
      args: 1,
      operation: ->(a) { +a },
    },
  }
end

Instance Attribute Details

#notation ⇒ Object (readonly)

Returns the value of attribute notation.



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# File 'lib/latex_eval/postfix_notation.rb', line 3

def notation
  @notation
end

#operations ⇒ Object (readonly)

Returns the value of attribute operations.



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# File 'lib/latex_eval/postfix_notation.rb', line 3

def operations
  @operations
end

Instance Method Details

#eval(subs = {}) ⇒ Object 



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# File 'lib/latex_eval/postfix_notation.rb', line 43

def eval(subs = {})
  stack = []

  notation.each do |elem|
    if elem.is_a? Symbol
      if operations.has_key? elem
        stack.push operations[elem][:operation].call(*stack.pop(operations[elem][:args])).to_f
      else
        stack.push subs[elem].to_f
      end
    else
      stack.push elem.to_f
    end
  end

  return stack.first
end