The question is about modeling infinity in C++ for the double data type. I need it in a header file, so we cannot use functions like numeric_limits.
Is there a defined constant that represents the largest value?
floating point numbers(such as doubles) can actually hold positive and negative infinity. The constant INFINITY should be in your math.h header.
Went standard diving and found the text:
4 The macro INFINITY expands to a constant expression of type float representing positive or unsigned infinity, if available; else to a positive constant of type float that overflows at translation time.
In Section 7.12 Mathematics <math.h>
Then of course you have the helper function isinf to test for infinity(which is also in math.h).
7.12.3.3 The isinf macro
int isinf(real-floating x);
Description: The isinf macro determines whether its argument value is an infinity (positive or negative). First, an argument represented in a format wider than its semantic type is converted to its semantic type. Then determination is based on the type of the argument.
Returns: The isinf macro returns a nonzero value if and only if its argument has an infinite value.