NaN behaves strangely in a boolean expression

[herme063]

I am using MathParser.org-mxparser 6.1.0, and with the below expressions I am getting strange results:

formula	results
[NaN] == 1	NaN
[NaN] == 1 && 0 == 0	NaN
[NaN] == 1 && 1 == 0	0
if([NaN] == 1 && 0 == 0, 1, 2)	NaN
if([NaN] == 1 && 1 == 0, 1, 2)	2

I have checked a few programming languages handling of NaN and the equality operator returns false (for C# and Java).
So I was expecting [NaN] == 1 to return 0 above instead of NaN.

What is the logic behind this result?

Also why is the 3rd expression returning 0, compared to the 2nd which is returning NaN?

[mariuszgromada]

"a == b" behaviour: return NaN if a is NaN or b NaN]

"a && b" behaviour: F- False, T - True, N - NaN

AND_TRUTH_TABLE = {
		/*		  F  T  N
		/* F */	{ F, F, F} ,
		/* T */	{ F, T, N} ,
		/* N */	{ F, N, N}
	};

So I think I have a small bug :-)

Thank you!