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Re: Re: Debracketing array symbols

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92197] Re: [mg92159] Re: Debracketing array symbols
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Tue, 23 Sep 2008 07:29:08 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

Clear[A]

Head[A[1]]

A

A = Array[a, {4}]

{a(1),a(2),a(3),a(4)}

Head[A[1]]

{a(1),a(2),a(3),a(4)}

Consequently, if A were defined using A vice a on the RHS there would be an infinite recursion


Bob Hanlon

---- carlos at Colorado.EDU wrote: 

=============
> deBracket[x_] :=
>  x /. A_Symbol[n__Integer] :>
>    ToExpression[
>     StringJoin[Prepend[ToString /@ {n}, ToString[A]]]]
>
> X[1] // deBracket
>
> X1
>
> {A[1], A[2], A[3], A[4]} // deBracket

Elegant.

A related question   A={A[1], A[2], A[3], A[4]}  produces infinite
recursion in 4.2 and 5.2 (NB - I prepare all coursework with
4.2 for compatibility with some remote students in industry)
 Is the symbol A used on the RHS?
{A[1], A[2], A[3], A[4]} //FullForm   just shows
List[A[1],A[2],A[3],A[4]]  which does not tell me much.
Where is the role of A in the RHS explained in the documentation?.






--

Bob Hanlon



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