RPN Calculator Ruby matching in arrays -

i'm making reverse polish notation calculator. wrote out gameplan , trying fill in. i'm @ part want take integers in array , move them new array (using shift remove permanently array).

this should easy can't figure out. tried identifying integers-only things

integer.match(x) x.class == integer 

but that's not working. i've tried building pull that's not in operations array, like, 1 fails:

x.include?(operations) 

i new , not @ coding. if you'd berate me how code sloppy or posted wrong, has. i'm trying. thanks,

class rpncalculator     def initialize(problem)         @problem = problem     end      def resolve         array = @problem.split(" ")         @array = array         operations = ["+", "-", "*"]         @operations = operations         queue = []         @queue = queue          array.map! { |x| /[0-9]/.match(x) ? x.to_i : x}          array.each |x|            #this i'm building & failing               array.shift(x)             queue << x         end      end # iterate through array # if array elements don't match operations element, push them queue # once have match on function, launch method # make 3 new rpn methods, 1 each + - * # method launched should affect last 2 items in queue. # result of method gets pushed end of queue.  # return remaining value in queue answer  # placeholder method + # placeholder method - # placeholder method *  end  test = "1 3 +" mytest  = rpncalculator.new(test) mytest.resolve 

cj, want @ error messages.

integer.match(x)   #=> nameerror: undefined local variable or method `x' main:object 

ruby assuming match class method of class integer. before sending match , match's argument x integer evaluates x , finds neither method or local variable; hence exception. is, have not defined x.

had defined x (as method or local variable), ruby have given different error message:

integer.match(4)   #nomethoderror: undefined method `match' integer:class 

that's because had not defined class method class integer. if had written

class integer   def self.match(x)     2 * x   end end 

ruby have been happy clam:

integer.match(4) #=> 8 

let's move on method, rubyists write two-space indents.

def resolve   array = @problem.split(" ")   @array = array   operations = ["+", "-", "*"]   @operations = operations   queue = []   @queue = queue    array.map! { |x| /[0-9]/.match(x) ? x.to_i : x}    array.each |x|      #this i'm building & failing      array.shift(x)     queue << x   end      end 

there problem right away in first line:

array = @problem.split(" ")   #nomethoderror: undefined method `split' nil:nilclass 

what error message mean? first, let's see irb can tell receiver of method split:

@problem       #=> nil @problem.class #=> nilclass 

now once again @ error message. says have not defined method split instance nil of class nilclass. split defined class string (i.e., string#split), receiver of split must string.

there more problems code, difficult deal without foundation of comes before. hope comments may have cleared part of problem, however.

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