Use of delayed assignment, :=, with a list

*To*: mathgroup at smc.vnet.net*Subject*: [mg91747] Use of delayed assignment, :=, with a list*From*: phillman5 <PHILLMAN5 at gmail.com>*Date*: Sun, 7 Sep 2008 05:35:08 -0400 (EDT)

I use simple 2x2 matrixes for each item in a optical train to get the over all 2x2 matrix. The four elements are a, b, c, d, and I can assign them easily in one step. {{a, b},{c, d}} = any 2x2 matrix however some times the rhs has variables, so I'd like to use an delayed assignment {{a, b},{c, d}} := any 2x2 matrix this does not work, Mathematica says the two lists are not the same shape. In particular: {{a, b},{c, d}} := {{1, zomeasure}, {-(1/f), 1 - zomeasure/f}} where f and zomeasure are variables (maybe not even defined yet). Mathematica says the lists are not the same shape, but if I use an assignment operator there is no problem. I am not completely convinced it is a mere Mathematica notation misunderstanding on my part because a simpler 2x2 assignment: {{q, g}, {h, k}} := {{f, w}, {r, t}} works. (Mathematica does respond {{Null, Null}, {Null, Null}}, but g does have a delayed assignment of w. Is there an easier way to do a delayed assignment than each member, a, b, c, d individually tempmatrix := {{1, zomeasure}, {-(1/f), 1 - zomeasure/f}} a := tempmatrix[[1]][[1]] b := . . .