Deleting a DownValue, Evaluate[f@@argList]=. does not do it
- To: mathgroup at smc.vnet.net
- Subject: [mg20744] Deleting a DownValue, Evaluate[f@@argList]=. does not do it
- From: hanssen at zeiss.de
- Date: Wed, 10 Nov 1999 00:17:53 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Hi, MathGroup, f[1]=1; f[2]=2; ?f yields "Global`f" f[1] = 1 f[2] = 2 now get rid of definition for 1 f[1]=.; ?f yields "Global`f" f[2] = 2 So far, it works as expected. I want to memorize results for combinations of arguments like f[a,b,c]=results and so on. To do this, I write f@@argList. Now I demonstrate this on lists with length 1, to make it simple. When making the assignment, it has to be wrapped in Evaluate: Clear[f]; Evaluate[f@@{1}]=1; Evaluate[f@@{2}]=2; ?f yields "Global`f" f[1] = 1 f[2] = 2 as before. Now I want to get rid of the definition for 1 in the analogous way: Evaluate[f@@{1}]=. yields Unset::usraw: Cannot unset raw object ! $Failed How to proceed without searching through DownValues[f] and deleting the one meant - very awkward? kind regards Dipl.-Math. Adalbert Hanszen