How about if they enter `5` `0` `ENTER` it sets th...

# rx

[michaelzinn]

How about if they enter 5 0 ENTER it sets the number state to 5, then it multiplies the number by ten and adds 0 to it, then it pushes the 50 onto the stack and resets the number state to 0… The immutable calculator state object would include a stack and a number. That state would “mutate” like in your example code.