[வெள்ளி டிசம்பர் 13, 2024] Fraga, Eric wrote:
> Response below/inline for email Visuwesh wrote:
>> (original email sent 13 Dec 2024 at 14:32)
>>
>> Update x := 3 and y first. Then update `a' and `z'. `z' will be 10.6.
>> Now update x := 2, and update `z' and `a'. `z' updates to 5.4 as shown
>> above but `a' remains 9!
>
> Yes, this is expected behaviour. Calc assumes a sequential evaluation,
> especially when the same variable is given a value more than once. It's
> not like most modelling languages which look at the ensemble of
> equations simultaneously.
I assumed this was the case. It does make sense when you take the whole
picture together. You are likely to use the same variable name (such as
T for temperature) everywhere so it would be best to use the nearest
one.
> [...]
>
>> Which begs the question: what should be `x'?
>
> Ideally, it would follow the Calc convention and would be the value last
> given (before point, where the table is), I guess.
When we have
x := 3
| 1 | 3 |
#+TBLFM:$2=$x
x := 6
| 1 | 6 |
#+TBLFM:$2=$x
value of `x' for the first table should be 3, and for the second 6.
However, when we have something like
x := 3
a := 2 * x
x := 2
z := 0.5 * x
| 1 | |
#+TBLFM:$2=$x*$z
what should $2 evaluate to? $z is straight-forward: $z=1. But what
about $x? Should it be 2 or 3? If we go by Calc's convention, it
should be 3. Do you agree?
> But, at least, for simple cases where variables are not overwritten,
> what you have done would be sufficient (and a really nice addition to
> the Calc package!).
>
> I intend to use it for sure.
I am glad to be of help, and hope the quick hack actually works
reliably.
