handling unary minus for shunting-yard algorithm
algorithm, rpn, shunting-yard
Solution
The way I did this years ago was invent a new operator for my postfix expression. So when I encountered a unary minus in the infix, I'd convert it to `#`. So my postfix for `a + -b` became `ab#+`.
And, of course, my evaluator had to know that `#` only popped one operand.
Kind of depends on how you're using the postfix expression once it's built. If you want to display it then your special `#` operator would probably confuse people. But if you're just using it internally (which I was), then it works great.
Problem
Is there a better way to handle unary "-" in converting a infix expression to a postfix one? The obvious one would be prefix every unary "-" with a 0. Does anyone know better implementation? Thanks!