Class: LatexEval::Equation

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

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(equation) ⇒ Equation 



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# File 'lib/latex_eval/equation.rb', line 6

def initialize(equation)
  @equation = equation
  @binary_key = {
    "+" => {
      symbol: :add,
      priority: 0,
      right_priority: false
    },
    "-" => {
      symbol: :subtract,
      priority: 0,
      right_priority: false
    },
    "*" => {
      symbol: :multiply,
      priority: 1,
      right_priority: false
    },
    "/" => {
      symbol: :divide,
      priority: 1,
      right_priority: false
    },
    "%" => {
      symbol: :mod,
      priority: 1,
      right_priority: false
    },
    "^" => {
      symbol: :power,
      priority: 2,
      right_priority: true
    }
  }
  @unary_key = {
    "-" => {
      symbol: :negative,
    },
    "+" => {
      symbol: :positive,
    },
  }
end

Instance Attribute Details

#binary_key ⇒ Object (readonly)

Returns the value of attribute binary_key.



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# File 'lib/latex_eval/equation.rb', line 4

def binary_key
  @binary_key
end

#equation ⇒ Object (readonly)

Returns the value of attribute equation.



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# File 'lib/latex_eval/equation.rb', line 4

def equation
  @equation
end

#unary_key ⇒ Object (readonly)

Returns the value of attribute unary_key.



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# File 'lib/latex_eval/equation.rb', line 4

def unary_key
  @unary_key
end

Instance Method Details

#postfix_notation ⇒ Object 



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# File 'lib/latex_eval/equation.rb', line 50

def postfix_notation
  out = []
  bank = []
  bracket = []
  unary = []

  # start with an assumed array
  bank.push []
  bracket.push []
  unary.push []

  equation.gsub(" ", "").split(/([%\)\(\^*+-\/])/).each do |value|
    if value != "" 
      if value == "("
        bank.push []
        bracket.push []
        unary.push []
      elsif value == ")"
        last = bracket.pop()
        bracket.last.concat last
        bracket.last.concat bank.pop().reverse.map { |e| binary_key[e][:symbol] } 
        bracket.last.concat unary.pop().reverse.map { |e| unary_key[e][:symbol] }
      elsif unary_key.has_key? value and (bracket.last.empty? || bracket.last.length == bank.last.length)
        unary.last.push value 
      elsif binary_key.has_key? value
        num_popped = 0
        bank.last.reverse_each do |b|
          if (binary_key[b][:right_priority] ? binary_key[b][:priority] > binary_key[value][:priority] : binary_key[b][:priority] >= binary_key[value][:priority])
            num_popped += 1
          else
            break
          end
        end
        bracket.last.concat unary.pop().reverse.map { |e| unary_key[e][:symbol] }
        unary.push []
        bracket.last.concat bank.last.pop(num_popped).reverse.map { |e| binary_key[e][:symbol] }
        bank.last.push value
      else
        if /[a-zA-Z]+/.match(value)
          bracket.last.push value.to_sym
        else
          bracket.last.push value.to_f
        end
      end
    end
  end

  out.concat bracket.pop()
  out.concat unary.pop().reverse.map { |e| unary_key[e][:symbol] }
  out.concat bank.pop().reverse.map { |e| binary_key[e][:symbol] }

  return out
end