IP (version 0.1.4)

Arithmetic: Methods for IP arithmetic

Description

Methods for unary and binary IP arithmetic

Usage

-e1
  e1 + e2
  e1 - e2

Value

an object of either an 'IPv4', 'IPv6' or 'IP' class

Arguments

e1

an object of either an 'IPv4', 'IPv6' or 'IP' class

e2

either a corresponding object of class 'IPv4', 'IPv6', 'IP' or an integer or a numerical vector

Details

Both IPv4 and v6 sets are represented as unsigned integers and are closed under addition and subtraction. An operation resulting in a negative number (or an overflow) is marked as NA. Operations are currently not always commutative. IP*-IP* are but those involving integers or floats are not. Thus, adding (or subtracting) an integer or a float to an IP* object will work but the reverse (adding (or subtracting) an IP* to an integer or a float) will raise an error (see example below and the caveat section in the package description). In addition multiplication and division are not implemented and will raise an error. Arithmetic operations involving IP* are better done using methods provided. Both IPv4 and IPv6 addresses are represented as unsigned integers but R only works with 32 bits signed integers. In addition, double precision numbers cannot represent all integers in the 0-(2^128-1) range. Therefore, converting an IPv6 object to numeric may cause a loss of precision and the same applies to arithmetic operations on IPv6 represented as floating point numbers.

Examples

##
ipv4("192.0.0.1") + 1
ipv6("fd00::1") + 1
ip(c("192.0.0.1", "fd00::1")) + 1

##
## Prohibited Arith operations
##
## this raises an error 
tryCatch(1L - ipv4("192.0.0.1"), error=function(e) e )
## and so will 
tryCatch(1 + ipv6("fd00::1"), error=function(e) e )
## as well as
tryCatch(ipv4("192.0.0.1") * 2, error=function(e) e )

##
## Loss of precision in arithmetical operations
##
(2^52 +1)- 2^52
(2^53 +1)- 2^53
##
identical((2^64 +1)- 2^64  , 0 )
## ...and so on
( (2^64 + 2^11 ) - (2^64))
## next representable number with IEEE 754 double precision floats; mind the gap
( (2^64 + 2^12 ) - (2^64))


## OTH,
((ipv6('::1') %<<% 53L) + ipv6('::1')) - (ipv6('::1') %<<% 53L)
##
(x <- ( ( ipv6('::1') %<<% 64L ) + ( ipv6('::1') %<<% 11L ) ) - ( ipv6('::1') %<<% 64L ) )
log2(as.numeric(x))