Hi!

I use 'alias' to define variable dependencies.

But when I want to use the result of my calculation as an expression, I bite the dust; I cannot get rid of the dependencies.

Can anyone help me here?

In the simplified example below, I use the independent variables z[3] and z[4] to define z[1](z[3],z[4]) and z[2](z[3],z[4]).

I then introduce a function f[1](z[3],z[4]) and its derivatives df_dz.

I introduce the names dz[1]/dz[3]=Dp[1,3], dz[1]/dz[4]=Dp[1,4] etc...

When I have calculated df_dz[3], however, I cannot insert values of z[2] without affecting Dp[2,3].

Actually, now I have finished my calculation and want df_dz[2,3] to be a regular expression, so that I can insert values of

z without affecting the Dp:s.

How can I convert df_dz[3] to a regular expression?

alias( seq(z[i]=z[i](seq(z[j],j=3..4)),i=1..2)):

alias(f=f(seq(z[j],j=3..4))):

alias(seq(seq(Dp[m,n]=diff(z[m](seq(z[j],j=3..4)),z[n]),m=1..2),n=3..4)):

f:=z[1]-z[2]*z[3]:

for j from 3 to 4 do

df_dz[j]:=diff(f,z[j]);

od:

df_dz[3];

subs(z[2]=4711,df_dz[3]);

whattype(Dp[1,3]);

whattype(z[3]);

*function*

* indexed*