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Re: [bug-gawk] Error Gawk Manual FP Precision
From: |
arnold |
Subject: |
Re: [bug-gawk] Error Gawk Manual FP Precision |
Date: |
Sun, 19 Aug 2018 00:24:39 -0600 |
User-agent: |
Heirloom mailx 12.4 7/29/08 |
Hi.
Thanks for your note. In the future, PLEASE send in plain text
format, not HTML, or at the very least, text and HTML.
Thanks.
On to your note:
> Dear bug-gawk:
>
> The section on comparing two floating point values correctly recommends
> making avoiding simple equality comparisons in favor of ensuring the
> values are close enough.
>
> The code given in 15.4.1.2 "Be Careful Comparing Values" is clearly
> wrong, though:
>
> 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
>
> If the desired value, a is -1000, and b is +1000, the answer is off by
> 2000. But difference will be zero.
You are correct. I will look at revising the documentation.
Thanks for pointing this out.
Arnold