Assignments and References

Assignment statements will be processed like any expressions with binary operators, however its first operand is handled differently than the second operand (which is the same as operands of other binary operators).  Consider the expression with its RPN translation:

A + B  A B +

During run-time, the value for the variable A is pushed onto the evaluation stack followed by the value of variable B. When the add operator is executed, it pops the two values off of the stack, adds them, and then pushes the resulting value back onto the stack. Now consider an assignment expression with its RPN translation:

A = B  A B =

During run-time, the assignment operator needs to know where to store the value being assigned. So, for the A operand, a reference to the variable value needs to be pushed onto the evaluation stack instead of its value. The assignment operator will not be pushing anything back onto evaluation stack.

The assignment operator will always be the last operator to be processed, so to handle multiple assignments, the multiple references will be pushed onto the evaluation stack. The assignment operator will simply keep popping references and assigning the value until the stack is empty.