Infinity

Write a function which tests if infinity is supported for floating point numbers (this step should be omitted for languages where the language specification already demands the existence of infinity, e.g. by demanding IEEE numbers), and if so, returns positive infinity. Otherwise, return the largest possible number.

For languages with several floating point types, use the type of the literal constant 1.0 as floating point type.

C++

#include <limits>

double inf()
{
  if (std::numeric_limits<double>::has_infinity)
    return std::numeric_limits<double>::infinity();
  else
    return std::numeric_limits<double>::max();
}

J

Positive infinity is produced by the primary constant function _:
It is also represented directly as a numeric value by an underscore, used alone.

Java

Java does not have a test for the existence of infinity, but it does have the concept in the Double class.

Double infinity = Double.POSITIVE_INFINITY; //defined as 1.0/0.0
Double.isInfinite(infinity); //true

As a function:

public static double getInf(){
   return Double.POSITIVE_INFINITY;
}

The largest possible number in Java is also in the Double class.

Double biggestNumber = Double.MAX_VALUE;

Its value is (2-2^-52)*2¹⁰²³ or 1.7976931348623157*10³⁰⁸ (a.k.a. "big"). Other number classes (Integer, Long, Float, Byte, and Short) have maximum values that can be accessed in the same way.