question on how to do this

*To*: mathgroup at smc.vnet.net*Subject*: [mg131314] question on how to do this*From*: d.a.paxton at gmail.com*Date*: Thu, 27 Jun 2013 06:32:15 -0400 (EDT)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-outx@smc.vnet.net*Delivered-to*: mathgroup-newsendx@smc.vnet.net

If you take an old idea like long multiply of binary numbers. You know the shift down to the left idea and then do an add on the columns. As you go along adding the columns how do you do this algebraically? You move along and if the column sum is odd you put a one down and if even you put a zero down. Then take the rest of the number and shift it and then add it to the next column. If I want to do this as an equation so I can do an inverse function. Not if mod shift go to the next column. Any ideas? Dave.