C++ cmath log() function
Example
Return the natural logarithm of different numbers:
const double E = 2.718281828;
cout << log(6.0f);
cout << log(E);
cout << log(2.0);
cout << log(1.0);
cout << log(0.0);
cout << log(-1.0f);
Definition and Usage
The log() function returns the natural logarithm of a number.
The log() function is defined in the <cmath> header file.
The natural logarithm is the logarithm with base e. The value of e is approximately 2.718282. Some implementations of the <cmath> library include a constant M_E but it is not guaranteed to be available.
Syntax
One of the following:
log(double number);log(float number);Parameter Values
| Parameter | Description |
|---|---|
| number |
Required. Specifies the value to calculate the logarithm for. If the value is negative, it returns NaN (Not a Number). If the value is 0, it returns -infinity. If this is an integer type then it will be treated as a double.
|
Technical Details
| Returns: | A float value (if the argument is float) or double value (in any other case) representing the natural logarithm of a number. |
|---|
