Question

What do you understand by pre- and post-conditions of a function?
Write the pre- and post-conditions to axiomatically specify the following
functions:
(a) A function takes two floating point numbers representing the sides of
a rectangle as input and returns the area of the corresponding
rectangle as output.
(b) A function accepts three integers in the range of -100 and +100 and
determines the largest of the three integers.
(c) A function takes an array of integers as input and finds the minimum
value.
(d) A function named square-array creates a 10 element array where
each all elements of the array, the value of any array element is
square of its index.
(e) A function sort takes an integer array as its argument and sorts the
input array in ascending order.

Answer 1

Pre-condition is the condition under which function will operate correctly.

Post-condition is the result after function is executed.

Answer a

Assuming function takes two floating point numbers a and b

Pre-condition - a > 0 && b > 0

Post-condition - area == a*b

Answer b

Assuming function takes three integer numbers a, b and c

Pre-condition - a, b and c are in range of -100 and 100

(a >= -100 && a <=100) && (b >= -100 && b <=100) && (c >= -100 && c <=100)

Post-condition -

largest = a (if a is largest)

largest = b (if b is largest)

largest = c (if c is largest)

largest = a (if all are same)

Answer c

Assuming function takes array of integers

Pre-condition - array size must be greater than 0

Post-condition - print minimum element

Answer d

Pre-condition - no pre-condition as there is no condition to be true for its execution.

Post-condition - create array of 10 elements with having value as square of index.

Answer e

Pre-condition - array size must be greater than 0

Post-condition - sorted array in ascending order