compoisson (version 0.3)

com.logspace: Operations in Log-space

Description

Computes the difference of two values in log-space.

Usage

com.log.difference(x, y)
	com.log.sum(x, y)
	com.log.factorial(x)

Arguments

x

first value

y

second value

Value

The requested computation in log-space.

Details

com.log.difference computes the difference of two values in log-space, $log( e^x - e^y )$, without significant chance of overflow or underflow.

com.log.sum computes the sum of two values in log-space, $log( e^x + e^y )$, without significant change of overflow or underflow.

com.log.factorial computes $log(x!)$ which is equivalent to a summation.

Examples

	a = exp(com.log.difference(log(100), log(20))); # a = 80
	b = exp(com.log.sum(log(100), log(20))); # b = 120
	c = exp(com.log.factorial(4)); # c = 24