### 19.7 Mathematical Constants

— Built-in Variable: I
— Built-in Variable: J
— Built-in Variable: i
— Built-in Variable: j

> A pure imaginary number, defined as `sqrt (-1)`. These built-in variables behave like functions so you can use the names for other purposes. If you use them as variables and assign values to them and then clear them, they once again assume their special predefined values See Status of Variables.

— Built-in Variable: Inf
— Built-in Variable: inf

> Infinity. This is the result of an operation like 1/0, or an operation that results in a floating point overflow.

— Built-in Variable: NaN
— Built-in Variable: nan

> Not a number. This is the result of an operation like 0/0, or ``Inf - Inf`', or any operation with a NaN.

> Note that NaN always compares not equal to NaN. This behavior is specified by the IEEE standard for floating point arithmetic. To find NaN values, you must use the `isnan` function.

— Built-in Variable: pi

> The ratio of the circumference of a circle to its diameter. Internally, `pi` is computed as ``4.0 * atan (1.0)`'.

— Built-in Variable: e

> The base of natural logarithms. The constant e satisfies the equation `log` (e) = 1.

— Built-in Variable: eps

> The machine precision. More precisely, `eps` is the largest relative spacing between any two adjacent numbers in the machine's floating point system. This number is obviously system-dependent. On machines that support 64 bit IEEE floating point arithmetic, `eps` is approximately 2.2204e-16.

— Built-in Variable: realmax

> The largest floating point number that is representable. The actual value is system-dependent. On machines that support 64-bit IEEE floating point arithmetic, `realmax` is approximately 1.7977e+308

— Built-in Variable: realmin

> The smallest normalized floating point number that is representable. The actual value is system-dependent. On machines that support 64-bit IEEE floating point arithmetic, `realmin` is approximately 2.2251e-308