PureBasic Forums - English

Posted: **Fri Feb 09, 2024 4:32 pm**

ASM and C-backend test ...

Define.d Number, Number2 = 1.2

; ASM OK, C-Backend Bug?
Number = Sqr(-1)
If Number = NaN()
  Debug "If / Ok: Number = NaN()"
Else
  Debug "Else / Bug: Number = NaN()"
EndIf

; ASM OK, C-backend Ok
Number = Sqr(-1)
If IsNAN(Number)
  Debug "If / Ok: IsNaN(Number)"
Else
  Debug "Else / Bug: IsNaN(Number)"
EndIf

; ASM Bug, C-Backend Bug
Number2 = 1.2
If Number = Number2
  Debug "If / Bug: Number = Number2"
Else
  Debug "Else / Ok: Number = Number2"
EndIf

Posted: **Fri Feb 09, 2024 6:00 pm**

mk-soft wrote:

Code: Select all

; ASM OK, C-Backend Bug?
Number = Sqr(-1)
If Number = NaN()
[...]

Wrong code. In order to check for NaN, only use PB's IsNaN() function.

Documentation wrote: NaN is a special value. Testing for it should not be done using normal comparisons because there are actually many different values for NaN and whether or not NaN is considered equal with itself in comparisons depends on the hardware.

Posted: **Fri Feb 09, 2024 6:25 pm**

Wiki: NaN=x false

Posted: **Fri Feb 09, 2024 8:37 pm**

The inequality of NaN against NaN is the early version of the IsNaN check. So if x <> x it is NaN. But it should be the same on all backends.

PureBasic Forums - English

NaN() and if compare problem

NaN() and if compare problem

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Re: NaN() and if compare problem

Re: NaN() and if compare problem