issue with a number float

Question

I have a problem with my float variable, i have to do some operation and then i have a final number what I saw is that some time the number is not correct, but just for a point for example when i have this number and i try to print it i don't give me back the same number:

float myNumber = 27589353.0f; NSLog(@"My Number is %.2f", myNumber);

the result is: My Number is 27589352.00

I've tried to put the variable double but i have the same issue.

@rmaddy "I've tried to put the variable double but i have the same issue." — user529758
– user529758, Commented Oct 30, 2013 at 0:30
@H2CO3 Oops - I guess I didn't make it to the last line. My bad. :) — rmaddy
– rmaddy, Commented Oct 30, 2013 at 0:32
@rmaddy I understand, it's quite tiring to read the same (or similar) questions agin and again. The brain says "whoops I've seen this before" and just substitutes things before actually reading. That's how it works out :) — user529758
– user529758, Commented Oct 30, 2013 at 0:34

Duncan C · Accepted Answer · 2013-10-30 01:14:29Z

The problem is that floats do not have enough precision, as maddy said in the comments above.

And this code:

double myNumber = 27589353.0f; NSLog(@"My Number is %.2f", myNumber);

Won't work either because the "f" qualifier on the constant forces the number to be a float, causes the loss of precision, then promotes the value to a double, once the damage is done.

This code however, will work correctly:

double myNumber = 27589353.0; NSLog(@"My Number is %.2f", myNumber);

(Note that I'm assigning a floating point value with a decimal, but no final "f"

Mirko Catalano · Accepted Answer · 2013-10-30 01:22:29Z

-1

try like that it's work, you have to remove the 'f' as well

double myNumber = 27589353.0; NSLog(@"My Number is %.2f", myNumber);

edited Oct 30, 2013 at 1:22

answered Oct 30, 2013 at 0:41

Mirko Catalano

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6 Comments

Duncan C Over a year ago

That's not right either. You are making myNumber a long integer, which can't store floating point values. That tap-dances around the issue. See my post below for the solution.

Hot Licks Over a year ago

(Or see my comment above. You couldn't even get it right after copying that.)

Mirko Catalano Over a year ago

when i post my answer the comment is not there -.- I have answer a similar answer a couple of days ago, @DuncanC what i tell Him is just that the problem is the 'f' so now i'm update my answer you can remove your -1 -.-

Hot Licks Over a year ago

You answered 38 minutes ago, my comment was 42 minutes ago. And just how is %.2ld going to format a double?

Mirko Catalano Over a year ago

I don't want still nothing you can see that i'm answer a same answer some days ago -.-

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