Re: Deleting Selective DownValues
- To: mathgroup at smc.vnet.net
- Subject: [mg63998] Re: [mg63984] Deleting Selective DownValues
- From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
- Date: Fri, 27 Jan 2006 05:13:09 -0500 (EST)
- References: <200601260843.DAA22208@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
On 26 Jan 2006, at 08:43, David Park wrote:
> Dear MathGroup,
>
> Suppose I have established the following definitions for f, but not
> necessarily in the given order.
>
> Clear[f]
> f[x_, y_, z_] := x y z
> f[a_, b_] := a b
> f[x_] := x
> DownValues[f]
> {HoldPattern[f[x_, y_, z_]] :> x y z, HoldPattern[f[a_, b_]] :> a b,
> HoldPattern[f[x_]] :> x}
>
> Now I would like to delete the f definition that has a given number
> of arguments, say f[a_,b_] with 2 arguments. So I need a routine:
>
> deleteDownValue[label_Symbol,numberOfArgs_Integer?Positive]:= ???
>
> which would reset DownValues[label] to eliminate any definition
> with numberOfArgs arguments.
>
> I have trouble with doing the matches and evaluation sequences. Can
> anyone help with this? Many thanks in advance.
>
> David Park
> djmp at earthlink.net
> http://home.earthlink.net/~djmp/
>
How about something much simpler:
In[1]:=
Clear[f]
f[x_, y_, z_] := x*y*z
f[a_, b_] := a*b
f[x_] := x
DownValues[f]
Out[5]=
{HoldPattern[f[x_, y_, z_]] :> x*y*z,
HoldPattern[f[a_, b_]] :> a*b, HoldPattern[f[x_]] :> x}
In[6]:=
f[x_, y_] =.
In[7]:=
DownValues[f]
Out[7]=
{HoldPattern[f[x_, y_, z_]] :> x*y*z,
HoldPattern[f[x_]] :> x}
??
Andrzej Kozlowski
- References:
- Deleting Selective DownValues
- From: "David Park" <djmp@earthlink.net>
- Deleting Selective DownValues