Worksheet 4: Assertions and Invariants Name:
An Active Learning approach to Data Structures using C
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Worksheet 4: Assertions and Invariants
In Preparation: Read Chapter 3 to learn more about debugging, testing and proving
correctness.
In Chapter 3 you learned how assertions and invariants can be used to prove a function or
algorithm is correct. In this worksheet you will practice those skills by writing invariants
for a number of different algorithms. Write the invariants and assertions that could be
used to prove each of the following programs correct. Outside of class in your homework
you will develop proofs of correctness by writing the arguments that link each invariant
to the next.
double min (double [ ] data, int n) {
double m = data[0];
assert (n > 0);
while (i = 1; i < data.length; i++) {
if (data[i] < m)
m = data[i];
}
return m
}
int factorial (int n) {
int f = 1;
assert (n > 0);
for (int i = 1; i <= n; i++) {
f = f * i;
}
return f;
}
