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MathGroup Archive 2000

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controlling evaluation

  • To: mathgroup at smc.vnet.net
  • Subject: [mg24530] controlling evaluation
  • From: richard nathan linger <rlinger at students.uiuc.edu>
  • Date: Mon, 24 Jul 2000 03:04:10 -0400 (EDT)
  • Organization: University of Illinois at Urbana-Champaign
  • Sender: owner-wri-mathgroup at wolfram.com

In[1]:=
func[x_][_] := x

In[2]:=
func[0][Print["bad"]]

"bad"

Out[2]=
0

Is there any way to modify the definition of func such that the Print
statement doesn't evaluate?  Setting the Attributes of func only changes
how x is handled.

For those who may care, I'm playing with combinators.  I want to be able
to use the Y combinator for recursion, but this won't work unless I can
eventually get it on the unchosen side of a branch statement (via the
combinators K[I] or K).  If at all possible, I would like to avoid
wrapping all my combinators with some HoldAll-attributed head.

Nathan Linger


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