Question

Exchange the contents:

Given two glasses marked A and B. Glass A is full of apple drink and glass B is full of grape drink. Write the specification for exchanging the contents of glasses A and B, and write a sequence of assignments to satisfy the specification.

Answer 1

Let the variables a, b, c represent Glass A, Glass B and Glass C and a, b, c can store values APPLE, GRAPE or EMPTY. 

Specification:

1. exchange (a, b) 

2. – – inputs: a, b : = APPLE, GRAPE 

3. – – outputs: a, b : = GRAPE, APPLE

Algorithm: