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MathGroup Archive 2007

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Re: The Mathematica equivalent of Cons (as in Lisp)?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73947] Re: The Mathematica equivalent of Cons (as in Lisp)?
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Sat, 3 Mar 2007 01:16:43 -0500 (EST)
  • References: <es90f4$2gc$1@smc.vnet.net>

Hi,

even when Mathematica call  data  {a,b,c}
a list, it is not a list in the sense of LISP.
The LISP list is in Mathematica {a,{b,{c,{}}}}
and the cons() function would be

Cons[a_,lst_List]:={a,lst}

Prepend[] will prepend an element to a Mathematica
list (that is essential an array).

In LISP cons() is a very quick operation, while
Prepend[] in Mathematica must copy the full list
to construct a new array with the prepended element.
So , cons() in LISP take always the same time
independent of the length of the list, but the
time for Prepend[] in Mathematica grow linear
with the length of the list.

Regards
   Jens


wooks wrote:
> For the benefit of someone with a Scheme background.
> 
> Would it be Prepend. Are there any pitfalls to be wary of?
> 
> 


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