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MathGroup Archive 2005

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Re: Reevaluation of conditional arguments when the condition has changed

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61056] Re: Reevaluation of conditional arguments when the condition has changed
  • From: "Jens-Peer Kuska" <kuska at informatik.uni-leipzig.de>
  • Date: Sun, 9 Oct 2005 01:35:05 -0400 (EDT)
  • Organization: Uni Leipzig
  • References: <di7r8p$koj$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

expr1 /. DownValues[foo]

Regards

  Jens



PS: This seems to be a bug, introduced by some 
kind of optimization.



"David Park" <djmp at earthlink.net> schrieb im 
Newsbeitrag news:di7r8p$koj$1 at smc.vnet.net...
| Dear MathGroup,
|
| Here is a programming problem that stumps me. We 
start with a condition that is always False.
|
| fooQ[_] := False
|
| Then write a definition that will factor out 
multipliers of fooQ objects.
|
| foo[a_ b_?fooQ] := a foo[b]
|
| The following does not factor because b, or 
anything else, fails the test.
|
| expr1 = foo[a b]
| giving: foo[a b]
|
| Now I define b as a fooQ object.
|
| fooQ[b] := True
|
| Now when I enter the same expression the a 
factors out.
|
| foo[a b]
| giving: a foo[b]
|
| But if I reevaluate expr1 the definition is not 
applied.
|
| expr1
| giving:  foo[a b]
|
| Why shouldn't I expect that to evaluate and now 
factor? Is there a proper way to write the 
definitions so it will evaluate?
|
| David Park
| djmp at earthlink.net
| http://home.earthlink.net/~djmp/
|
| 



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