Hello
I am inclined to share Samuel point of view: this is a compliocation
than could be avoided.
But I cannot resist noting that the annoucement is 6 years older than
the announcement of the weapon of mass destruction that consist in
changing the behaviour of the addition of a matrix with a null matrix.
Sorry for insisting, but I will again call for the removal from the
final Scilab 6.0 release of this planned change.
First, I am not convinced at all by the argument put forward that it
will make Scilab more consistent with other language such as Matlab,
Octave, Julia.. : after all, every language has its indiosycrasies; a
Matlab user will yet have to adapt herslef to this change, bu along
many other ones; and I,do not think that changing this behavour will
convice any Matlab user to switch to Scilab nor prevent anyone
thinking about switching to give up because of this beahviour.
Second The argument that it enhances Scilab internal consistency is a
little bit more compelling, but not much: after all, addition and
subtraction are different operations from multiplication and division,
such one can justify different behaviour. And there are cases when it
make tho code more compact.
Adnd lastly both arguments are anyway swept away by the simple fact
that the change should make all previous code unreliable: you cannot
be sure in advance that the working of your program has not been
affected by the change (and the warning that is designed to alert to
the user is not sufficient: a warning can easily be missed, especially
for second hand users not so famaliar with Scilab and if it is hidden
among many other warnings).
I hope that the Scilab will come to its senses and give up making this
change.
Regards.
Éric.
2016-02-18 18:45 GMT+01:00 Samuel Gougeon <[email protected]
<mailto:[email protected]>>:
Hello,
Le 29/03/2010 11:40, Bruno JOFRET a écrit :
Hi,
Please find attached SEP #40 talking about Cell Arrays.
This SEP is targeting Scilab 6.0 as we will introduce a new
syntax for cells.
Any feedbacks are welcome.
6 years after, it is very (very) late to comment or make any
suggestion.
Yet, Scilab 6.0 is not yet released, so i hope that this won't be
too late for the essential:
Indexation (extraction and insertion) with {} should really not be
introduced.
This message comes after first comments and rational recently
posted there:
http://mailinglists.scilab.org/Scilab-users-a-i-j-specific-extraction-syntax-with-should-not-be-introduced-tp4033484.html
As another way to explain why {} extractors and inserters must not
be introduced,
we may follow the pages of the current version of the SEP
available here:
http://gitweb.scilab.org/?p=scilab.git;a=blob;f=SEP/SEP_040_cell_arrays.odt
* After a cell array *c = { %pi %i %t ; %z "abc" list(1,%s)}*
has been (very friendly) built with the new {} heterogeneous
concatenator:
o the *extraction of the content of any single cell
component* should be direct:
+ with Scilab < 6 : c(5).entries or c(1,3).entries
+ with Scilab >=6: c(5) or c(1,3)
+ with Scilab < 6 : c(5) or c(1,3)
+ with Scilab >=6: {c(5)} or {c(1,3)}
Whenever any wrapped-in-cell answer would be needed,
it still can be obtain by packaging the answer,
instead of implementing a "dereferencing" way to
address a content through a very specific {}
extractors and inserters when unwrapped values are
required.
o As well, *the insertion into a single component must be
direct, and any type of data should be accepted*:
+ Scilab < 6: c(5).entries = ["Hi" "Hello"] or
c(1,3).entries = ["Hi" "Hello"]
+ Scilab >=6: c(5) = ["Hi" "Hello"] or c(1,3) = ["Hi"
"Hello"]
So, page 4:
# c = cell([4,3,2]); for i = 1:24, c*{i}* = i, end
becomes
# c = cell([4,3,2]); for i = 1:24, c*(i)* = i, end
o Is there any reason to not address cells components simply
as we do for matrix components, directly with (i,j,..)? I
do not find any.
The .entries addressing was needed due to the encoding of
cells as mlists. But what could motivate keeping any
intermediate level to access to the values of data, for
extraction as well as for insertion? I do not see a single
reason.
As noted here-above, from the fact that the LHS object is
a cell array, any data type can be accepted and inserted,
without any prior packaging of the RHS as a cell array.
The wrapping in cell must be done internally by the
insertion process.
o Then, Scilab 6: c(5) = {"abcd"} will insert a true
elementary cell as the c(1,3) c's component, not the
string "abcd". This is a straightforward and very clear
syntax. What is in RHS parameter is just values that are
inserted in the array, *as is*.
* *The SEP does not present **_insertion and extraction of
multiple components_ in a once*.
After still *c = { %pi %i %t ; %z "abc" list(1,%s)}, *the
current implementation is the following:
o *multiple insertion*: *a) of corresponding multiple
components*:
+ c(:,1) = { %e "zz" }
assigns %e to c(1,1) and "zz" to c(2,1) /in a
distributive way/!
1. This kind of distributive assignment is a very
great new feature!!
2. The assignment is transparently done using
/linearized indices/. unmatching sizes/formats of
the recipient and of the source is smoothly
handled. Here, a row of cells feeds a column of
cells. This is nice as is! This behavior could
also be implemented with other types of RHS
containers, at least for a list. So
+ c(:,1) = list(%e, "zz")
should do the same. But it does not:
--> c(:,1) = list(%e, "zz")
Wrong insertion: A Cell expected: use {...} instead of
(...).
This feature might be implemented later. This is not
so urgent as removing the {} addressing.
If this feature is implemented, how will it be
possible to insert a list in a single component?
# c(3) = list(list(%t)) // will do it. Or if the
size of the list is not 1, even
# c(3) = list(%t, %z) // mismatch could be
handled softly in a comprehensive way
+ c([1 2]) = { %e "zz" } does the same using a vector of
linearized indices. Great!
o *multiple insertion*: *b) of a single component to be
replicated*:
+ c([1 4]) = {"abc"} inserts the same "abc" string at
the 1st and 4th positions in c. This is great! The
only thing is that the syntax should become simply
c([1 4]) = "abc"
In the final implementation that we suggest and hope,
c([1 4]) = {"abc"} will be as well possible but will
insert the cell {"abc"} instead of the string "abc" at
the desired positions.
o *multiple extraction:*
+ c(1,:) returns{%pi %i %t}: this is great! By
default, this can't be anything else than a cell array.
No c{1,:} syntax is required
+ c(:,3) returns {%t ; list(1,%s)}: still great and
expected!
No c{3,:} syntax is required
+ c(1:2,[1 3]) returns {%pi %t ; %z list(1,%s)} as
expected.
No c{1:2,[1 3]} syntax is required
+ with a linearized index: c([2 5 3]) returns {%z ; %t ;
%i} column cell, as with matrices addressed with a
linearized index a column is returned: Great!
No c{[2 5 3]} syntax is required
* Finally, *what about conversions between a cell array and a
list? *We think that this kind of conversion between these 2
types of containers should be available in Scilab.
o *list => cell* :
+ If it becomes possible to feed a cell array (or
subarray) with a list as discussed above, then this
kind of conversion won't need anything else. We will
just have to do:
c = cell(2,3); c(:) = list(%pi, %z, %i, "abc", %t,
list(1,%s))
+ Otherwise: *makecell() *should be kept and renamed
*list2cell()*, instead of being removed. It already
works as expected :
L = list(%pi, %z, %i, "abc", %t, list(1,%s));
--> makecell([2 3], L(:))
ans =
[1x1 constant] [1x1 polynomial] [1x1 constant]
[1x1 string ] [1x1 boolean ] [ list ]
o *cell => list:*
+ The present special extraction with {:} does it, but
this syntax must be removed. Keeping it only for that
is meaningless:
--> typeof(c{:})
ans =
list
+ A new *cell2list()* converter should rather be
implemented.
Hoping that this will convince you to remove the {} complicated
addressing and the related data wrapping,
Best regards
Samuel Gougeon
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