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Programming Trivia Pop Quiz: Be Different!

Unlike the last question, this one should be common knowledge for everybody.

 

QUESTION: Find a value that will cause the boolean to be TRUE when the code is executed.

 

BeDifferent.png


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This one is too easy

Spoiler
There is not a number that will return TRUE here.Smiley Wink

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answer:

Spoiler
might this be a trick question?
i know that you cannot guarantee x + (y+z) == (x+y)+z for floating points,
but to compare the same number/bit-representation against each other should never be different.

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@jwscs wrote:

answer:

Spoiler
 
Spoiler
Spoiler
might this be a trick question?
i know that you cannot guarantee x + (y+z) == (x+y)+z for floating points,
but to compare the same number/bit-representation against each other should never be different.

If you look at the definition of floating point numbers, there is a case where it SHOULD be different.

 

 

 

That condition is what Christian is trying to teach us about with this trivia question.

 

Ben

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ok found it...

Spoiler
thought about NaN .. but searched for a constant, didn't enter my mind before to just write it in 😉
strange-math2.png

guess from mathematical standpoint it makes sense, since the value is undefined
links: https://en.wikipedia.org/wiki/IEEE_754#Formats
https://stackoverflow.com/questions/1565164/what-is-the-rationale-for-all-comparisons-returning-fals...

 


If Tetris has taught me anything, it's errors pile up and accomplishments disappear.
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My first guess was either +inf or -inf.  Interestingly enough, this returns false.  I guess you could prove that a double precision float is countably infinite...

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@BownM i must disagree with you, since you only have a finite number of bytes for the representation, it follows, that there can only be a finite number of different numbers.


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According to IEEE-754, there is exactly one unique bit pattern for +inf and -inf, respectively. However, there is a huge number of different NaNs. (details)


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@jwscs wrote:

@BownM i must disagree with you, since you only have a finite number of bytes for the representation, it follows, that there can only be a finite number of different numbers.


Approximately 18.4*10^18 unique combinations. 🙂

/Y

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    • input value:NAN

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