# ln

operator

 Library: Floating point number support (OMFLOAT) Import : omfloat.xmd Library: Binary coded decimal numbers (OMBCD) Import : ombcd.xmd Returns: the natural logarithm of a floating point or bcd number

Declaration
```define overloaded external float function
ln value float x

ln value bcd x
```

Purpose

Use ln to calculate the natural logarithm (logarithm to the base e), of either

• a floating point number, or
• a BCD number

You must import either omfloat.xmd or ombcd.xmd in your program. Decide whether you want BCD mathematics (excellent for financial calculations) or floating point mathematics (excellent for extremely large numbers). The function argument must be greater than zero.

### Floating Point Example:

```  ; Displays the natural logarithm of 10  as a floating point number.
import "omfloat.xmd" unprefixed
process
local float x-var initial {"10"}
local float result

set result to ln (x-var)
output "Natural logarithm of " || "d" % x-var || " = " || "d" % result || "%n"
; Output: "Natural logarithm of 10 = 2.302585092994046".
```

### BCD Example:

```  ; Multiply x and y by adding their natural logarithms.
; In this case, display the product obtained by adding the natural logarithms of 100 and 50.
import "ombcd.xmd" unprefixed
process
local bcd  x initial {"100"}
local bcd  y initial {"50"}
local bcd lnx
local bcd lny
local bcd product-from-ln

set lnx to ln (x)
set lny to ln (y)
set product-from-ln to exp(lnx + lny)
output "Product of 100 times 50 from adding natural logarithms = "
|| "d" % product-from-ln
|| "%n"
; Output: "Product of 100 times 50 from adding natural logarithms = 4999.9999999999967158"

```

If the result of a natural logarithm does not fit in the data type of the argument, the value returned is truncated to fit the data type.

If you calculate the natural logarithm of an integer, you need to coerce the integer - to a floating point or BCD number - so that the appropriate function is called. The result will depend on which logarithm function is called.

In an OmniMark program, always surround operators with spaces.

Related Topics
Other Library Functions