Non Commutative Multiply

*To*: mathgroup at smc.vnet.net*Subject*: [mg128593] Non Commutative Multiply*From*: Rodrigo AP <digorna at gmail.com>*Date*: Thu, 8 Nov 2012 02:09:06 -0500 (EST)*Delivered-to*: l-mathgroup@mail-archive0.wolfram.com*Delivered-to*: l-mathgroup@wolfram.com*Delivered-to*: mathgroup-newout@smc.vnet.net*Delivered-to*: mathgroup-newsend@smc.vnet.net

Dear group, I want to multiply two matrices, for example, A = {{e, f}, {g, h}} B = {{a, b}, {c, d}} Using A.B, Mathematica returns {{a e + b g, a f + b h}, {c e + d g, c f + d h}} I would like to get, however, the following result: {{e a + f c, e b + f d}, {g a + h c, g b + h d}} since, for me, the entries {a,b,c,d,e,f,g,h} are operators, i.e., they are non-commutative. I could solve this problem clearing the attribute "Orderless" in the built-in function Times: ClearAttributes[Times, Orderless] I know, however, this can be dangerous. I tried to define a function Times2[a_,b_]:=Times[a,b] and then use ClearAttributes[Times2, Orderless] but it doesn't work. How could I solve this problem? Thanks in advance Rodrigo

**Follow-Ups**:**Re: Non Commutative Multiply***From:*Bob Hanlon <hanlonr357@gmail.com>