*gawk:* Comparing FP Values

15.4.1.2 Be Careful Comparing Values
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Because the underlying representation can be a little bit off from the
exact value, comparing floating-point values to see if they are exactly
equal is generally a bad idea. Here is an example where it does not
work like you would expect:
$ gawk 'BEGIN { print (0.1 + 12.2 == 12.3) }'
-| 0
The general wisdom when comparing floating-point values is to see if
they are within some small range of each other (called a "delta", or
"tolerance"). You have to decide how small a delta is important to you.
Code to do this looks something like the following:
delta = 0.00001 # for example
difference = abs(a) - abs(b) # subtract the two values
if (difference < delta)
# all ok
else
# not ok
(We assume that you have a simple absolute value function named 'abs()'
defined elsewhere in your program.)