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More robust pattern based replacement rules?

• To: mathgroup at smc.vnet.net
• Subject: [mg120765] More robust pattern based replacement rules?
• From: Irretrev Unable <irdeva_ble at yahoo.com>
• Date: Tue, 9 Aug 2011 07:20:42 -0400 (EDT)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com

I'm trying to come up with a method for creating somewhat more robust pattern based replacement rules.  I've cooked up the following simple example:

simpRule = a b v___ - c d v___ -> e v

a b - c d /. simpRule 

produces e

- a b + c d /. simpRule

produces - a b + c d

Is there a way to write one simpRule that can handle both cases?

(The actual rule I'm trying to create has to match more terms with a leading coefficient that is more complicated than a simple minus sign, but I figure that for an initial post I should stick with a simple question.)

Thanks in advance.

• Follow-Ups:
  • Re: More robust pattern based replacement rules?
    • From: Leonid Shifrin <lshifr@gmail.com>