Returns the natural logarithm of its argument. This produces slightly more accurate results than the otherwise equivalent expression log(e,(argument)).

Format: Ln(exprn)

Arguments:

- exprn (float>: Expression to compute the natural logarithm of.

Return type: float

Error conditions: Returns 'Bottom' if exprn evaluates to 'Bottom', or if exprn is not positive.

Example:

`value = ln(time)
; Sets value to the natural logarithm of the player's statetime.`