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Re: ClearAll error message

  • To: mathgroup at smc.vnet.net
  • Subject: [mg92389] Re: ClearAll error message
  • From: carlos at Colorado.EDU
  • Date: Tue, 30 Sep 2008 07:35:41 -0400 (EDT)
  • References: <gbnpep$pr3$1@smc.vnet.net> <gbqcv3$ebb$1@smc.vnet.net>

Actually this was not a big deal.  The group working with the program was
puzzled by the message but soon it was fixed. BTW, one student came
with an elegant one-liner to create a nxn symmetric array:

  S=Table[rootname[Min[i,j],Max[i,j]],{i,n},{j,n}]

The Clear behavior seems largely a question of esthetics.  One of the basic
rules of functional programming is function composition equivalence:

        y:=f(x); z:=g(y)    equiv    z:=g(f(x))

Since   name=Symbol["A"]; ClearAll[name] is not equivalent
to   ClearAll[Symbol["A"]] the rule is violated here, and likewise
for any function with HoldAll attribute.  Correct?


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