Am I missing something? This is from try.jsonata.org but it certainly is the same in Node-red. This should be 'false', right?
You can see the same thing in JavaScript:
$ node
Welcome to Node.js v16.13.1.
Type ".help" for more information.
> 1.1-1>0.1
true
When you evaluate 1.1-1 you can see what is happening:
> 1.1-1
0.10000000000000009
Welcome to the way JavaScript represents floating point numbers.
2 Likes
Thank you! I thought I was going crazy 
Not javascript alone...
pi@nrpi:~ $ python3
Python 3.6.3 (default, Apr 26 2019, 12:57:09)
[GCC 6.3.0 20170516] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 1.1-1
0.10000000000000009
>>>
2 Likes
Interesting. PowerShell gets it right.
> 1.1-1
0.1
And then screws it up!
> 1.1-1 -gt 0.1
True
> 1.1 -gt 1.1
False
R also messes up. As does Lua and PHP. Got bored after that!
1 Like
haha yeah, its an float thing. Unfortunately you have to know this to um, know this 
So where it "looks" like powershell gets it right, whats likely happening is it rounds (for display) after x amount of decimal places (e.g. 0.10000000000000009 is rounded to 0.10000000 which is then shown as 0.1) but the actual number is still 0.10000000000000009 therefore 1.1 - 1 == 0.10000000000000009 and then 0.10000000000000009 -gt 0.1 == true. I'd rather be told 1.1 - 1 == 0.10000000000000009 then at least i can understand why 1.1-1 -gt 0.1 == true
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It's still wonky 1.1-1 = 0.1, where does that 9 come from lol
walked into that one! maybe i should change my profile pic to my foot!
It is just how floating point math works. I'm sure all of these programs are using the same C compiler.
$ perl -e 'printf "%0.30f\n", $_ for 1.1-1.0, 0.1, 13.1-13'
0.100000000000000088817841970013
0.100000000000000005551115123126
0.099999999999999644728632119950
Its not a compiler issue, it is an IEEE 754 design issue. You only have 64 bits to fit an almost infinite amount of numbers into. It simply has limitations.
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It's a design issue. There's BCD and there's fixed-point arithmetic. But for some reason, they chose to go with floating-point.
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