NSDecimalNumber doubleValue incorrect for digit 7

Asked Jan 12 '17 at 18:44

Active Jan 12 '17 at 18:55

Viewed 154 times

How can I store '0.07' value except NSDecimalNumber? I mean I can't using NSDecimalNumber because when I'm using doubleValue function, decimal 0.07 becomes 0.0699999... double or something else, but never 0.07 double :)

Example from debugger:

(lldb) po [[NSDecimalNumber alloc] initWithDouble:.07]
0.07000000000000001024

(lldb) po [[NSDecimalNumber alloc] initWithDouble:(double).07]
0.07000000000000001024

(lldb) po [[[[NSDecimalNumber alloc] initWithDouble:7] decimalNumberByDividingBy:[[NSDecimalNumber alloc] initWithDouble:100]] doubleValue]
0.069999999999999993

(lldb) po 0.07
0.070000000000000007

(lldb) po (double)0.07
0.070000000000000007

The only way to store 0.07 is NSDecimalNumber, but it's inconvenient:

(lldb) po [[[NSDecimalNumber alloc] initWithDouble:7] decimalNumberByDividingBy:[[NSDecimalNumber alloc] initWithDouble:100]]
0.07

edited Jan 12 '17 at 18:55

rmaddy

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asked Jan 12 '17 at 18:44

Vasilii Muravev

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Try creating your `NSDecimalNumber` from the string `@"0.07"`. – rmaddy Jan 12 '17 at 18:54
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there's no problem to create NSDecimalNumber, problem is to take double from decimal.... – Vasilii Muravev Jan 12 '17 at 18:59
1

See http://stackoverflow.com/questions/588004/is-floating-point-math-broken – rmaddy Jan 12 '17 at 19:01
yap, this is it, thank you – Vasilii Muravev Jan 12 '17 at 19:12
Also, if you need decimals down to only 2 digits, it is often good practice to use integers. – Mundi Jan 12 '17 at 19:34
Did you fix it? – anoop4real May 20 '19 at 13:43
@anoop4real Yes, see https://stackoverflow.com/questions/588004/is-floating-point-math-broken – Vasilii Muravev May 21 '19 at 16:13

NSDecimalNumber doubleValue incorrect for digit 7

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