Date: Jan 19, 2013 2:04 AM
Author: S.K.Mody
Subject: How to avoid wrong answers in simple arithmetic expressions.
I tried the following cody problem for fun:

[quot]

Given an amount of currency, return a vector of this form:

[100 50 20 10 5 2 1 0.5 0.25 0.1 0.05 0.01]

Example:

Input a = 257.68

Output b is [2 1 0 0 1 1 0 1 0 1 1 3]

Always use bigger bills/coins if possible.

[/quot]

My solution:

function b = makingChange(a)

v = [100 50 20 10 5 2 1 0.5 0.25 0.1 0.05 0.01];

for i = 1 : length(v)

b(i) = floor(a/v(i));

a = a - b(i)*v(i);

end

end

But, due to rounding error, this gives a wrong answer for example for a = 135.01.

The problem does not go away even if I replace the last line by a = rem(a, v(i)).

How does one avoid such issues in general?