CSL102: Introduction to Computer Science
II semester 2004-05

Assignment: Reversing an Integer using only integer operations

Develop an algorithm $revint: \mathbb{Z}\rightarrow \mathbb{Z}$ to reverse the digits of an integer (given in base 10).

Notes:

1. You are allowed to use only functions on integers in your algorithm.
2. The following examples should guide you on some special cases:

   $revint (0) = 0$

   $revint (-0148) = -841$

   $revint (1480) = 841$

Steps:

1. First develop the method and try to give a proof that it is correct.
2. Translate your method into SML and write an SML program to do the same.

Note:

1. You are not allowed to change any of the names given in the signature. You are not even allowed to change upper-case letters to lower-case letters or vice-versa.
2. You may define any new functions you like in the structure besides those mentioned in the signature.
3. Your program should work with the given signature.
4. You need to think of the most efficient way of implementing the various functions given in the signature so that the function results satisfy their definitions and properties.
5. Since the evaluator is going to look at your source code before evaluating it, you must explain your algorithms in the form of ML comments, so that the evaluator can understand what you have implemented.
6. Do not add any more decorations or functions or user-interfaces in order to impress the evaluator of the program. Nobody is going to be impressed by it.
7. There is a serious penalty for copying. If it is felt that there is too much similarity in the code between any two persons, then both are going to be penalized equally. So please set permissions on your directories, so that others cannot copy your programs.