removing rules from function definitions
- To: mathgroup at smc.vnet.net
- Subject: [mg33028] removing rules from function definitions
- From: Erich Neuwirth <erich.neuwirth at univie.ac.at>
- Date: Tue, 26 Feb 2002 04:35:19 -0500 (EST)
- Sender: owner-wri-mathgroup at wolfram.com
let me explain my problem with a simplified example
i define
f[1] := f[1] = 1
f[n_] /; n > 1 := f[n] = f[n - 1]*2
after evaluating f[1]
i have
In[36]:=
FullForm[DownValues[f]]
Out[36]//FullForm=
List[RuleDelayed[HoldPattern[f[1]],1],RuleDelayed[HoldPattern[f[2]],2],
RuleDelayed[HoldPattern[f[3]],4],RuleDelayed[HoldPattern[f[4]],8],
RuleDelayed[HoldPattern[f[5]],16],RuleDelayed[HoldPattern[f[6]],32],
RuleDelayed[HoldPattern[f[7]],64],RuleDelayed[HoldPattern[f[8]],128],
RuleDelayed[HoldPattern[f[9]],256],
RuleDelayed[HoldPattern[f[10]],Times[f[Plus[10,-1]],2]],
RuleDelayed[HoldPattern[Condition[f[Pattern[n,Blank[]]],Greater[n,1]]],
Set[f[n],Times[f[Plus[n,-1]],2]]]]
no i want to remove all the rules which were added during the
evaluation.
Drop[DownValues[f],MyPattern]
essentially allows me to create a new rules list,
but i cannot get MyPattern right
MatchQ[#,RuleDelayed[HoldPattern[f[_Integer],_Integer]]
does not work because HoldPattern gets evaluated,
but doing it Verbatim does not work either
because then _Integer is not evakuated and therefore does not work any
more.
i really ned a pattern matching all rules
RuleDelayed[HoldPattern[f[_Integer]],_Integer]
which interprets _Integer nonverbatim, but everything else verbatim.
can anybody help me?
--
Erich Neuwirth, Computer Supported Didactics Working Group
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