how implement a rule

*To*: mathgroup at smc.vnet.net*Subject*: [mg112568] how implement a rule*From*: Murray Eisenberg <murray at math.umass.edu>*Date*: Mon, 20 Sep 2010 05:43:34 -0400 (EDT)*Organization*: Mathematics & Statistics, Univ. of Mass./Amherst*Reply-to*: murray at math.umass.edu

I want to define a function abs (mimicking Abs) with various properties. One part of the definition is: abs[c_ z_ /; c \[Element] Reals] = Abs[c] abs[z] Given that, how might I express that abs[z] is always real in such a way that the result of abs[1/abs[z]^2] will be 1/abs[z]^2 -- WITHOUT explicitly introducing, say: abs/: abs[1/abs[z_]^2] = 1/abs[z]^2 ? -- Murray Eisenberg murray at math.umass.edu Mathematics & Statistics Dept. Lederle Graduate Research Tower phone 413 549-1020 (H) University of Massachusetts 413 545-2859 (W) 710 North Pleasant Street fax 413 545-1801 Amherst, MA 01003-9305