'Bug' with formatted printing ?

[DiscoPants]

Hello, I wonder if anybody can help? Below is a simple command to print a mathematical equation giving the correct return:-
> echo "a" | awk '{ print(70.57 * 100) }'
7057

If I try and format this using a decimal integer I get the wrong return:-
echo "a" | awk '{ printf("%d\n", 70.57 * 100) }'
7056

Is this a bug or is there someting I blatantly missing and should quit computers?

 

[CaKiwi]

The problem here is that 70.57 * 100 is not exactly equal to 7057 because of rounding errors. You can see this with the following program:

awk 'BEGIN{ printf("%20.16f\n", 70.57 * 100);exit }

which produced

7056.9999999999991000

One way around the problem in this case is to use

awk 'BEGIN{ printf("%.0f\n", 70.57 * 100);exit }

which rounds rather than truncates the argument. CaKiwi

"I love mankind, it's people I can't stand" - Linus Van Pelt

 

[DiscoPants]

Cheers mate, I'd decided to use a floating number too.

Just can't understand why multiplying a number with 2dp by 100 can go wrong!

Cheers!