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MathGroup Archive 2005

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Re: Converting a mapping into a well-defined function

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56525] Re: [mg56499] Converting a mapping into a well-defined function
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Thu, 28 Apr 2005 02:40:12 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

Your example output appears to violate your prohibition against sorting the 
result.

A={{a,5},{b,27},{a,14},{c,4},{e,94},{b,6},{d,9},{e,4}};

B=A//. {s___,{x_,y_},m___,{x_,_},f___}:>
      {s,{x,y},m,f}

{{a, 5}, {b, 27}, {c, 4}, {e, 94}, {d, 9}}


Bob Hanlon

> 
> From: "Gilmar" <gilmar.rodriguez at nwfwmd.state.fl.us>
To: mathgroup at smc.vnet.net
> Date: 2005/04/26 Tue PM 09:53:32 EDT
> To: mathgroup at smc.vnet.net
> Subject: [mg56525] [mg56499] Converting a mapping into a well-defined function
> 
> Dear Mathematica User Friends:
> 
> I need to build a module that takes a non-empty set A
> (whose elements are 2-tuples), and appends (or not) those 2-tuples
> to a set B  according to the following criteria:
> 
> (1.) if the abscissa of a 2-tuple in A is unique (among the abscissas
> of all the other 2-tuples in A), then the module appends that 2-tuple
> to the set B.
> 
> (2.) if there are n 2-tuples in A that share the same abscissa, then
> the module appends the first of those 2-tuples to B ("first" here means
> the first of such n 2-tuple encountered, as you read A from left to
> right),but does not append the rest to B.
> 
> (3.) the module does not attempt to sort the set B, after the appending
> process is completed.
> 
> Example:
> 
> If A = {{a,5},{b,27},{a,14},{c,4},{e,94},{b,6},{d,9},{e,4}}
> 
> then
> 
> B=Module[A]={{a,5},{b,27},{c,4},{d,9},{e,94}}.
> 
> Another way to re-phrase the above example;
> 
> if A defines a mapping:
> 
> A(a)=5, A(b)=27, A(a)=14, A(c)=4, A(e)=94, A(b)=6, A(d)=9, A(e)=4
> 
> them the module converts the mapping A into a well-defined function:
> 
> A(a)=5, A(b)=27, A(c)=4, A(d)=9, A(e)=94.
> 
> Thank you for your help!
> 
> 


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