This is an archived page from the Fall 2019 version of the course. For the latest version, see https://uvatoc.github.io.

Problem Set 5 Update

by David Evans and Nathan Brunelle

Two more updates to PS5:

  1. Problem 7 considered adding an array but not loops to NAND-CIRC. But, it doesn’t make sense to have arrays without any way to update the index used to access them. So, for this to make sense we need to also have an instruction to update i. So, we have modified this question to add conditional increment and decrement instructions:

    • CINC v takes a regular variable as its input, and if the value of v is 1 it updates the value of i to be i + 1. Otherwise (when v is 0), it does not do anything.

    • CDEC v takes a regular variable as its input, and if the value of v is 1 it updates the value of i to be max(i - 1, 0). Otherwise, it does not do anything.

  2. Since we didn’t get to examples of uncomputability proofs in class this week, we’re deferring Problem 9 and Problem 10 from PS5 to PS6. If you’ve already solved these, great - just save your solution to submit for the same questions that will be moved to PS6.