       Re: Implicit Times

• To: mathgroup at smc.vnet.net
• Subject: [mg128658] Re: Implicit Times
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Wed, 14 Nov 2012 01:30:06 -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
• References: <20121109000050.A731368E1@smc.vnet.net> <20121110070632.836E26951@smc.vnet.net> <k7p3di\$c9h\$1@smc.vnet.net>

```On 11/11/2012 20:56, Dave Snead wrote:
> Thanks, but the issue is not defining the operator.
> The issue is Mathematica's implicit assumption of a Times (*) when there's a
> space between variables.
> The NonCommutativeMultiply (**) already exists.
>
> So when I input
> x y//FullForm
> I want Mathematica to return
> NonCommutativeMultiply[x,y]
> Times[x,y]
>
> Of course I want the explicit Times (*) to
> still work the same as before,
> x*y//FullForm
> yielding
> Times[x,y]
>
>

I think you can probably get what you want, if you start with an
expression in the form of a string:

In:= str = " (b a) c*d"

Out= " (b a) c*d"

In:= str1 = StringReplace[str, "*" -> "\[SmallCircle]"]

Out= " (b a) c\[SmallCircle]d"

In:= expr =
ToExpression[str1, StandardForm, Hold] /. Times -> CircleTimes /.
SmallCircle -> Times // ReleaseHold

Out= (b\[CircleTimes]a)\[CircleTimes](c d)

In:= % // FullForm

CircleTimes[CircleTimes[b, a], Times[c, d]]

The above uses the standard Mathematica parser using a couple of tricks,
but more generally, if you start with a string, you can parse it as you
see fit with a little effort.

David Bailey
http://www.dbaileyconsultancy.co.uk

```

• Prev by Date: System of second-order nonlinear ordinary differential equations
• Next by Date: Re: Help with map /@
• Previous by thread: Re: Implicit Times
• Next by thread: Re: Implicit Times