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MathGroup Archive 2007

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Re: 2D pattern matching

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77252] Re: 2D pattern matching
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 6 Jun 2007 06:57:18 -0400 (EDT)
  • References: <f43dm5$f8$1@smc.vnet.net>


Hi Alex,

As your patterns spans more than one row, you must specify a global 

pattern for the whole array, Therefore, if you have more than one block 

of "1" you must use ReplaceRepeated. E.g. asssuming your array is in a:

a//.{x1:{__}..,{y1:___,1,1,y2___},{z1:___,1,1,z2___},x2:{__}..}->{x1,{y1,a1,a2,y2},{z1,a3,a4},x2}

hope this helps, Daniel





alexxx.magni at gmail.com wrote:

> hi everybody,

> 

> do you know how to do a pattern match involving 2D matrices?

> If e.g. you have a list

> 

> a = {{0, 0, 0, 0, 0, 0}, {0, 1, 0, 0, 0, 0}, {0, 1, 0, 1, 1, 0}, {0,

>    0, 0, 1, 1, 0}, {0, 0, 0, 0, 0, 0}, {0, 0, 0, 0, 0, 0}}

> 

> i.e.

> 0 0 0 0 0 0

> 0 1 0 0 0 0

> 0 1 0 1 1 0

> 0 0 0 1 1 0

> 0 0 0 0 0 0

> 

> is it possible for me to write a rule by which I am able to find the

> 2x2 square of 1's, and replace it with something else?

> 

> I studied all I could on patterns, but didnt find an answer...

> 

> thanks for ANY help

> 

> Alessandro Magni

> 

> 




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