Final answer:
An RPN can perform a controlled act when two conditions are met: a valid operator is applied to the correct number of operands and there are enough values on the stack for the operation to be performed.
Step-by-step explanation:
An RPN (Reverse Polish Notation) system can perform a controlled act when two conditions are met:
- A valid operator is applied to the correct number of operands. For example, in the RPN expression '2 3 +', the operator '+' is applied to the operands '2' and '3', resulting in the sum '5'.
- There are enough values on the stack for the operation to be performed. Each operand is pushed onto the stack, and when an operator is encountered, the required number of operands are popped from the stack to perform the operation.
These conditions ensure that operations in an RPN system are performed correctly and avoid errors.