Assertion failing on a simple double?

Asked Jan 29 '17 at 23:28

Active Jan 29 '17 at 23:28

Viewed 38 times

I have a simple method that takes 3 arguments (target balance, current balance, interest rate). The method is supposed to calculate the time it would take (in years) to reach the target balance. I know the formula is correct since it prints out correctly but it fails on a assertion for some reason.

Here is my code:

double count_years(double t, double b, double r); //Declaration
double account::count_years(double t, double b, double r) {
    double years = (1/(r/100)) * ((t/b) - 1);
    return years;
}

I'm checking the code using this as an assertion and getting an error:

assert(a.count_years(60, 50, 0.1) == 200);

Error Message:

assertion "a.count_years(60, 50, 0.1) == 200"

asked Jan 29 '17 at 23:28

Muhammad Ali

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Rounding error? – skypjack Jan 29 '17 at 23:30
You **DON'T** check floating point numbers for equality. Or if it's necessary google how to tackle it properly. – DeiDei Jan 29 '17 at 23:31
It's exactly 200 as I calculate it on a calculator and I have to check it using assertion as instructed by the assignment. – Muhammad Ali Jan 29 '17 at 23:32
1

a floating point value rarely exactly equals to an integer value. you should check against a range, such as abs(a.count_years(60,50,0.1) - 200) < 0.0001) – Shiping Jan 29 '17 at 23:32
Fixed it using a range, so is there no method of checking the exact value? – Muhammad Ali Jan 29 '17 at 23:36
@MuhammadAli You can't simply calculate the exact value to begin with in most languages. Read the dupe. – Baum mit Augen Jan 29 '17 at 23:37

Assertion failing on a simple double?

0 Answers0