       Re: Deleting more subtle then Clear[ ] ?

• To: mathgroup at smc.vnet.net
• Subject: [mg2273] Re: [mg2234] Deleting more subtle then Clear[ ] ?
• From: Allan Hayes <hay at haystack.demon.co.uk>
• Date: Thu, 19 Oct 1995 01:35:04 -0400

```alfred at ca-risc.co.at
in [mg2234] Deleting more subtle then Clear[ ] ?
I hope the following example may help.

f[x_,y_] := f[x,y] = x -y
Do[f[x,y], {x,1,2},{y,1,2}]

?f
Global`f
f[1, 1] = 0
f[1, 2] = -1
f[2, 1] = 1
f[2, 2] = 0
f[x_, y_] := f[x, y] = x - y

dv = DownValues[f]
{Literal[f[1, 1]] :> 0, Literal[f[1, 2]] :> -1,
Literal[f[2, 1]] :> 1, Literal[f[2, 2]] :> 0,
Literal[f[x_, y_]] :> (f[x, y] = x - y)
}

Now change DownValues by standard techniques.
For example

DownValues[f] =
Cases[dv,e_/;FreeQ[e, Literal[f[_?NumberQ,_?NumberQ]]]]

{Literal[f[x_, y_]] :> (f[x, y] = x - y)}

?f
Global`f
f[x_, y_] := f[x, y] = x - y

Allan Hayes
hay at haystack.demon.co.uk

*********
Begin forwarded message:

>From: alfred at ca-risc.co.at
>To: mathgroup at smc.vnet.net
>Subject: [mg2234] Deleting more subtle then Clear[ ] ?
>Organization: EUnet EDV DienstleistungsgesmbH, Wien

Well,
Let's assume we have a function f[x,y,z] where x and y are
VERY big or
time consuming lists of numbers or functions.
By defining f[x_,y_,z_]:= f[x,y,z] =   I make MMA remember
what it did.
How can I now tell it to disremember for all f[x,*,*] when I
specifically want
it to reprocess whatever is dependend on x (i.e. the contents of
the file has
changed but the name is the same) but NOT on y?

Thanks for help

Alfred
--
================================
Alfred H. Corrodi		"Capitalism is based on the assumption
Risk Manager			 that you can win the game. Communism
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alfred at ca-risc.co.at (NeXT)	 break even. Mysticism is based on the
Tel/43/1/531311967 Fax/5337341   assumption that you can leave the game."

```

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