# Comparing FP Values (The GNU Awk User’s Guide)

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#### 16.4.1.2 Be Careful Comparing Values

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 - 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.) If you write a function to compare values with a delta, you should be sure to use ‘`difference < abs(delta)`

’ in case someone passes in a negative delta value.