Because that’s how floating-point is defined (more generally than just Javascript). See for example: http://en.wikipedia.org/wiki/Floating-point#Infinities http://en.wikipedia.org/wiki/NaN#Creation Crudely speaking, you could think of 1/0 as the limit of 1/x as x tends to zero (from the right). And 0/0 has no reasonable interpretation at all, hence NaN.
double supports Infinity double inf = Double.POSITIVE_INFINITY; System.out.println(inf + 5); System.out.println(inf – inf); // same as Double.NaN System.out.println(inf * -1); // same as Double.NEGATIVE_INFINITY prints Infinity NaN -Infinity note: Infinity – Infinity is Not A Number.
Standardwise… In ECMAScript, addition of two nonzero finite numbers is implemented as (ECMA-262 ยง11.6.3 “Applying the Additive Operators to Numbers”): the sum is computed and rounded to the nearest representable value using IEEE 754 round-to-nearest mode. If the magnitude is too large to represent, the operation overflows and the result is then an infinity of … Read more
You can test if your implementation has it: #include <math.h> #ifdef NAN /* NAN is supported */ #endif #ifdef INFINITY /* INFINITY is supported */ #endif The existence of INFINITY is guaranteed by C99 (or the latest draft at least), and “expands to a constant expression of type float representing positive or unsigned infinity, if … Read more
In Python, you can do: test = float(“inf”) In Python 3.5, you can do: import math test = math.inf And then: test > 1 test > 10000 test > x Will always be true. Unless of course, as pointed out, x is also infinity or “nan” (“not a number”). Additionally (Python 2.x ONLY), in a … Read more