Log

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Log

Returns the natural logarithm; zero gives minus infinity and a negative gives NaN.

Syntax

Declare Function Log cdecl ( ByVal number As Double ) As Double

Parameters

• number

Description

There can be some confusion with this notation given that in mathematics the natural logarithm function is usually denoted LN, while the logarithm of base 10 is often denoted as LOG. FreeBASIC, like most computer programming languages, uses LOG to denote the natural logarithm. The required number argument can be any valid numeric expression greater than zero. If number is zero, FreeBASIC returns a special value representing "-infinity", printing like "-Inf". If number is less than zero, Log returns a special value representing "not defined", printing like "NaN" or "IND", exact text is platform dependent. If number is an uninitialized variable, -infinity is returned.

Log can be overloaded as operator to accept user-defined types.

Return Value

Returns the logarithm with the base e (also know as the natural logarithm) of number.

Remarks

Usage

result = Log( number )

Differences from QB

• None

See also

• Exp

Examples

'Find the logarithm of any base

Function LogBaseX (ByVal Number As Double, ByVal BaseX As Double) As Double

    LogBaseX = Log( Number ) / Log( BaseX )

    'For reference:   1/log(10)=0.43429448

End Function

Print "The log base 10 of 20 is:"; LogBaseX ( 20 , 10 )

Print "The log base 2 of 16 is:"; LogBaseX ( 16 , 2 )

Sleep

The output would look like:

The log base 10 of 20 is: 1.301029995663981
The log base 2 of 16 is: 4

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Category: Mathematical Functions
Kind: function

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Reproduced from the FreeBASIC Wiki Manual under the GNU Free Documentation License 1.3 — with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. Copyright © the FreeBASIC project and wiki contributors. See License.