unbelievable ...
- To: mathgroup at smc.vnet.net
- Subject: [mg16567] unbelievable ...
- From: schatzi <antoine.zahnd at iprolink.ch>
- Date: Wed, 17 Mar 1999 23:54:51 -0500
- Sender: owner-wri-mathgroup at wolfram.com
Hello,
I just came accross something that I *DO NOT* understand.
Let A be a structure with two componants x and y and xA and yA functions
that return its x and y
componants.
ClearAll[A,xA,yA]
xA[A[x_,y_]]:=x
yA[A[x_,y_]]:=y
So far everything is fine ...
{a=A[1,2],xA[a],yA[a]}
=> {A[1,2],1,2}
Now I would like to have a function which sets the x componant of a A
symbol.
I guess the following is not only far from the state of art, but deeply
wrong:
xASet[A[x_,y_],z_]:=(A[x,y]=A[z,y])
The first use seems ok:
{a,xASet[a,3],a}
=> {A[1,2],Null,A[3,2]}
But now it is impossible to reset a to A[1,2] (and only to A[1,2] !!!)
{a=A[1,2],a=A[1,5]}
=> {A[3,1],A[1,5]}
Thank you very much for your help.
antoine.zahnd at iprolink.ch