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Re: Length of a held expression

  • To: mathgroup at smc.vnet.net
  • Subject: [mg96528] Re: [mg96524] Length of a held expression
  • From: "David Park" <djmpark at comcast.net>
  • Date: Mon, 16 Feb 2009 06:53:05 -0500 (EST)
  • References: <7436629.1234686646764.JavaMail.root@m02>

b = Sequence[1, 2];
Length[Unevaluated@{b, 3}]
2


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/  


From: Nikolaus Rath [mailto:Nikolaus at rath.org] 

Hello,

How can I get the length of a list in a Hold[] expression? I.e. if

 b = Sequence[1,2];

then I want the length of {b,3} given as 2. But

 Length[{b,3}]

gives me the length after splicing in b (which is 4), while

 Length[Hold[{b,3}]]

gives me the length of the hold expression (which is 1).


Anyone able to help?


Best,

   -Nikolaus

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