# Ln()

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## Description

Returns the result of taking the natural logarithm (base e) of *number*. *number* may be a floating point number, and a floating point result is returned.

Related Topics: e(), exp(), log(), power().

## Examples

- > say ln(0)
- You say "-Inf"
- > say ln(1)
- You say "0"
- > say ln(e())
- You say "1"
- > say ln(10)
- You say "2.302585"

(--Soylent 01:43, 3 December 2005 (EST))

## Nifty Trick

It's not really a trick, but a well known math formula. Namely, the change of base formula:

ln X log_b X = ------ ln b

Or more generally:

log_c X log_b X = --------- log_c B

where *c* is a new sane value.

For example, if I wanted to know how many bits a certain value will take:

th ceil(fdiv(ln(value),ln(2)))