>
>
>f(s,t):=s[t];
>w:x;
>x[4]:5;
>f(w,4);
>
>it gives 5 but I, the user, suppose the definition f(s,t):=s[t] means for
> f(w,4) w[4] and not x[4].
> The global value of w as a symbol is incorrect here, we
>want to use the array w.
>
Is the function definition relevant here? Otherwise I would simplify the
example to
w:x;
x[4]:5;
w[4];
which gives 5 as expected. The meaning of w[4] is I think:
(1) w has no array property and is not a list so evaluate it.
(2) We now get x[4]. Since x has an array property we can evaluate x[4]
to get 5.
This seems to be confirmed by the following experiments.
w:x;
x[4]:5;
w:1;
w[4];
This give an error as evaluation of w yields 1[4].
w:x;
x[4]:5;
x:1;
w[4];
Now we get 5. w evaluates to x and since x has the array property,
x[4] evaluates to 5.
w:x;
x[4]:5;
x:[1,1,1,1,1,1,1,1];
w[4];
This is tricky! Now we still get 5. So maxima seems to prefer
the array property of x above its value which is a list.
w:x;
x:[1,1,1,1,1,1,1,1];
w[4];
Now x has no array property so its value is inspected. We get 1.
x[4]:5;
x:[1,1,1,1,1,1,1,1];
x[4];
We get 5. Maxima prefers again the array property.
Michel