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Things that are numbers:
- a memory address
- the letter B
- an error encountered when trying to open a file
- the concept of being false, as opposed to being true
Things that are not numbers:
- this particular floating-point
number
>> typeof(NaN) <- "number"It’s valid for C too, but it will be either a double or a float.
#include <cmath> #include <iostream> #include <numbers> int main() { decltype ( NAN ) f { std::numbers::pi }; std::cout << f << std::endl; }Dude, after forcing
-std=c++20, the compiler still can’t find a reference forstd::ostream::operator<<(float)…Do I have to link with some non-standard library? There doesn’t seem to have any
numbers.aincluded with gcc.Weird, it should be standard C++20. Hope are you invoking gcc?
godbolt link: https://godbolt.org/z/6Tn4Kcjrs
Edit: be sure to call g++, not gcc.
Oh, that’s right, I was using gcc.
Things that are numbers
…
the concept of being false, as opposed to being true
? If your’re referring to the C language convention that anything nonzero is ‘true’… false itself is exactly zero. Zero is a number. Perhaps I miss something here?
That’s what I’m saying.
Ah. OK. I re-read your comment :) Silly me.
accidentally double types the a and suddenly his program is baking flatbread
At least NaNs are different from each other and themselves.
SQL’s null would like a word here.
That makes sense though. Two things can be “not number” yet be different.
But two things cannot be “not number” and be the same.
And they should still fail == because that’s the behavior of IEEE 754 numbers.
