Re: Non Commutative Multiply

• To: mathgroup at smc.vnet.net
• Subject: [mg128606] Re: Non Commutative Multiply
• From: mstankus at gmail.com
• Date: Thu, 8 Nov 2012 19:01:30 -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
• References: <k7fm4l\$jko\$1@smc.vnet.net>

```On Wednesday, November 7, 2012 11:16:35 PM UTC-8, digo wrote:
> 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

You can use NCAlgebrq. See http://www.math.ucsd.edu/~ncalg/

Mark Stankus

```

• Prev by Date: Conformal Mapping
• Next by Date: Re: Non Commutative Multiply
• Previous by thread: Re: Non Commutative Multiply
• Next by thread: Re: Non Commutative Multiply